Positive Electrode Precursor

ABSTRACT

This positive electrode precursor includes: a positive electrode active material containing a carbon material and an alkali metal compound, wherein 5≤A≤35, when A (g/m 2 ) is a weight of the alkali metal compound in the positive electrode active material layer at one surface of the positive electrode precursor, 10≤B≤100 as well as 0.20≤A/B≤1.00, when B (g/m 2 ) is a weight of the positive electrode active material in the positive electrode active material layer, and 1≤C≤20, when C (m 2 /cm 2 ) is a specific surface area per unit area as measured by the BET method at one surface of the positive electrode precursor.

RELATED APPLICATION DATA

This application is a divisional application of U.S. application Ser.No. 15/761,085 filed on Mar. 16, 2018, which is a § 371 National StageApplication of PCT International Application No. PCT/JP2017/002006 filedJan. 20, 2017, which claims priority to Japanese Patent Application Nos.2016-010895 filed Jan. 22, 2016; 2016-155698 filed Aug. 8, 2016; and2016-155837 filed Aug. 8, 2016, the entire contents of each of theseapplications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a positive electrode precursor.

BACKGROUND ART

In recent years, a power smoothing system of wind power generation or amidnight power storage system, a household dispersive power storagesystem based on solar power generation technologies, a power storagesystem for an electric car, and etc. have been received attention fromthe viewpoint of effective utilization of energy aiming at conservationof global environment and resource saving.

The first requirement of a battery to be used in these power storagesystems is high energy density. Researches on a lithium ion battery havebeen energetically undergoing rapid development as a strong candidate ofa high energy density battery which is capable of responding to suchrequirements.

The second requirement is high output characteristics. For example, in acombined case of a highly efficient engine and a power storage system(for example, a hybrid electric car) or a combined one of a fuel celland a power storage system (for example, a fuel cell electric car), highoutput discharging characteristics in the power storage system have beenrequired during its acceleration.

At present, an electric double layer capacitor, a nickel-hydrogenbattery, and etc. have been undergoing development as a high outputstorage device.

Among the electric double layer capacitors, the one using an activatedcarbon as an electrode has output characteristics of about 0.5 to 1kW/L. This electric double layer capacitor has been considered to be themost suitable device in a field where the high output is required,because it also has high durability (cycle characteristics and storagecharacteristics at high temperatures). However, an energy densitythereof is only about 1 to 5 Wh/L. Then, further improvement of theenergy density has been necessary.

On the other hand, a nickel-hydrogen battery which has been adopted in ahybrid electric car at present has a high output equivalent to that ofthe electric double layer capacitor and an energy density of about 160Wh/L. However, energetic attempts have been made to further enhance theenergy density and output thereof as well as to enhance durability(particularly, stability at high temperatures).

Another attempts for a high output have also been made in lithium ionbatteries. For example, such a lithium ion battery has been developedwhich is capable of providing a high output of over 3 kW/L at 50% depthof discharge (the depth indicates a state of discharging of the storageelement in terms of percentage). However, the energy density thereof isequal to or lower than 100 Wh/L, i.e., it is designed to intentionallysuppress the high energy density which is the greatest characteristicsof the lithium ion battery. Durability (cycle characteristics andstorage characteristics at high temperatures) thereof is inferior tothat of the electric double layer capacitor. Therefore, it is limited tobe used in a narrower range of discharging depth of 0 to 100% to holdpractical durability. Since a practical capacitance is considered to befurther decreased, energetic researches have been made to furtherenhance the durability.

As described above, an application for practical use of the storageelement having a high energy density, high output characteristics, anddurability has been strongly required. However, each of these existingstorage elements has its merits and demerits. Namely, a new storageelement satisfying these technological requirements has been required.The storage element called a lithium ion capacitor, i.e., one ofnonaqueous hybrid capacitors has been received attention as a strongcandidate thereof, and researches on this have energetically undergonedevelopment.

A lithium ion capacitor (nonaqueous hybrid capacitor) is one of storageelements using a nonaqueous electrolytic solution containing a lithiumsalt, and carrying out charging and discharging, not only in thepositive electrode by non-Faraday reaction based onadsorption/desorption of anions which is similar to the case of theelectric double layer capacitor at equal to or higher than about 3 V,but also in a negative electrode by Faraday reaction based onocclusion/releasing of lithium ions which is similar to the case of thelithium ion battery.

In summarizing the aforementioned electrode materials andcharacteristics, the high output as well as high durability is bothrealized, however, the energy density is decreased (for example,assuming the density of one time) in the case where a material such asan activated carbon, etc. is used as the electrode, and charging anddischarging are carried out by adsorption/desorption (non-Faradayreaction) of ions at a surface of the activated carbon. On the otherhand, in the case where an oxide or a carbon material is used as theelectrode, and charging and discharging are carried out by Faradayreaction, the energy density is increased (for example, a density of tentimes obtainable by non-Faraday reaction using the activated carbon),however, problems occur in the durability and the outputcharacteristics.

The electric double layer capacitor as a combination of these electrodematerials has characteristics wherein an activated carbon (having anenergy density of one time) is used as a positive electrode and anegative electrode, charging and discharging at both of electrodesproceed by non-Faraday reaction, and an energy density (one time at thepositive electrode×one time at the negative electrode=1) is low in spiteof a high output as well as high durability.

The lithium ion secondary battery have characteristics wherein a lithiumtransition metal oxide (having an energy density of ten times) is usedas a positive electrode, a carbon material (having an energy density often times) is used as a negative electrode, and charging and dischargingat both electrodes proceed by Faraday reaction. However, it has aproblem in output characteristics and durability in spite of a highenergy density (ten times at the positive electrode x ten times at thenegative electrode=100). Furthermore, depth of discharging should berestricted to satisfy high durability which is required in a hybridelectric car, and 10 to 50% of the energy can only be used for thelithium ion secondary battery.

The lithium ion capacitor has characteristics wherein an activatedcarbon (having an energy density of one time) is used as a positiveelectrode, a carbon material (having an energy density of ten time) isused as a negative electrode, and charging at positive electrodeproceeds by Faraday reaction, although discharging at the negativeelectrode proceeds by non-Faraday reaction. It is a novel asymmetriccapacitor possessing the combined characteristics of the electric doublelayer capacitor as well as the lithium ion capacitor, and havingcharacteristics wherein a high energy density (one time at the positiveelectrode×ten times at the negative electrode=10), in spite of the highoutput and high durability, is exhibited, and the depth of dischargingis not needed to be restricted as is the case with the lithium secondarybattery.

In the lithium ion capacitor, superior I/O characteristics as well asand the high energy density is realized by pre-doping lithium in advanceto the negative electrode. Various methods with respect to thispre-doping method have been proposed. A method for supplying lithiumions to a negative electrode active material in the fastest and mostreliable way is to attach metal lithium on a surface of the negativeelectrode active material layer, and pour it into a nonaqueouselectrolytic solution.

As a pre-doping method using this metal lithium, there have beenproposed specifically, for example, the following methods.

In Patent Document 1, there has been proposed a pre-doping method bycrimping a metal lithium foil onto a negative electrode active materiallayer. However, the metal lithium foil, being now produced industrially,usually has a thickness of equal to or more than 30 μm. When acapacitance of the metal lithium foil having a thickness of equal to ormore than 30 μm is calculated from the theoretical capacitance (3.86Ah/m²) of metal lithium, it can contain lithium having a capacitance ofequal to or more than 61.9 Ah/m² per unit area. Accordingly, anexcessively thick negative electrode having a thickness of equal to ormore than 100 μm must be used to pre-dope a suitable amount of lithiumions to the negative electrode. A method for attaching a stripe-shapemetal lithium foil to the electrode is applied in replace of using suchan excessively thick negative electrode. According to this method,however, doping of lithium ions becomes unstable in the negativeelectrode.

Therefore, the pre-doping method using the metal lithium foil had aproblem of not exhibiting the high output of the element.

In Patent Document 2, there has been proposed a method for pre-dopinglithium ions to the negative electrode by decomposing lithium oxalate bycharging and discharging with addition of the lithium oxalate to thenegative electrode or the electrolytic solution. However, there is aproblem that the lithium oxalate which has low oxidation potentialcauses gas generation by gradual decomposition thereof, and remains inthe electrolytic solution or the negative electrode during a long periodof storage.

On the other hand, various investigations have been conducted on apositive electrode of the aforementioned storage element (particularly,the lithium ion secondary battery).

For example, in Patent Document 3, there has been proposed a lithium ionsecondary battery with the positive electrode containing lithiumcarbonate, and having a mechanism for interrupting the current inresponse to increase in internal pressure of the battery. In PatentDocument 4, there has been proposed a lithium ion secondary batteryusing a lithium composite oxide such as lithium manganate, etc. as thepositive electrode, and suppressing elution of manganese by containinglithium carbonate in the positive electrode. In Patent Document 5, therehas been proposed a method for oxidizing various kinds of lithiumcompounds in the positive electrode so as to recover the capacitance ofa deteriorated storage element. In Patent Document 6, there has beenproposed a method for containing a carbonate salt, a hydroxide, and asilicate salt as an antacid in the activated carbon positive electrode.In Patent Document 7, there has been proposed a method for suppressingcapacitance deterioration accompanied by charging and dischargingcycles, and increasing the initial capacitance by addition of lithiumcarbonate to a composite oxide containing lithium and nickel in thepositive electrode.

These methods, however, have not considered at all pre-doping to thenegative electrode in the nonaqueous hybrid capacitor, and there hasremained much room for enhancing efficiency of pre-doping and exhibitinga higher capacitance of the nonaqueous hybrid capacitor.

PRIOR ART DOCUMENTS Patent Documents

-   [Patent Document 1] Japanese Patent Publication No. 4738042-   [Patent Document 2] Japanese Patent Publication No. 3287376-   [Patent Document 3] Japanese Unexamined Patent Publication No.    H4-328278-   [Patent Document 4] Japanese Unexamined Patent Publication No.    2001-167767-   [Patent Document 5] Japanese Unexamined Patent Publication No.    2012-174437-   [Patent Document 6] Japanese Unexamined Patent Publication No.    2006-261516-   [Patent Document 7] Japanese Unexamined Patent Publication No.    2001-84998

Non-Patent Documents

-   [Non-patent Document 1] E. P. Barrett, L. G. Joyner, and P.    Halenda, J. Am. Chem. Soc., 73,373 (1951)-   [Non-patent Document 2] B. C. Lippens, J. H. de Boer, J. Catalysis,    4319 (1965)-   [Non-patent Document 3] R. S. Mikhail, S. Brunauer, E. E. Bodor, J.    Colloid Interface Sci., 26,45 (1968)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been proposed in view of the status quo.

The problem to be solved by the present invention is to provide thepositive electrode precursor composed of the carbon material and thealkali metal compound for the nonaqueous hybrid capacitor which iscapable of not only carrying out pre-doping to the negative electrode ina short time by promoting decomposition of the alkali metal compound,but also having a high capacitance; and to provide the production methodof the nonaqueous hybrid capacitor which is capable of pre-dopinglithium ions to the negative electrode without using metal lithium, andhaving less gas generation during storage at high temperatures as wellas excellent charging and discharging cycle characteristics under a highload.

Means for Solving the Problems

The present invention has been accomplished based on this knowledge.

Namely, the present invention has the following constitutions:

[1] A positive electrode precursor comprising a positive electrodeactive material containing a carbon material and an alkali metalcompound,

wherein 5≤A≤35, when A (g/m²) is a weight of the alkali metal compoundin the positive electrode active material layer at one surface of thepositive electrode precursor,

10≤B≤100 as well as 0.20≤A/B≤1.00, when B (g/m²) is a weight of thepositive electrode active material in the positive electrode activematerial layer, and

1≤C≤20, when C (m²/cm²) is a specific surface area per unit areameasured by the BET method at one surface of the positive electrodeprecursor.

[2] The positive electrode precursor according to [1], wherein thealkali metal compound is the compound selected from the group consistingof an alkali metal carbonate salt, lithium oxide, and lithium hydroxide.[3] The positive electrode precursor according to [1], wherein thealkali metal compound is an alkali metal carbonate salt, and thecarbonate salt is one or more kinds selected from lithium carbonate,sodium carbonate, potassium carbonate, rubidium carbonate, and cesiumcarbonate.[4] The positive electrode precursor according to [3], wherein at leastlithium carbonate is contained in an amount of equal to or more than 10%by weight in the alkali metal compound.[5] The positive electrode precursor according to [3] or [4],

wherein 5≤X≤50, when X % by weight is a weight ratio of the alkali metalcompound in the positive electrode active material layer of the positiveelectrode precursor,

5≤S₁≤60, and 0.50≤S₁/X≤2.00, when S₁% is an area of oxygen whoseluminance values are binarized based on the average luminance value inthe oxygen mapping of the surface of the positive electrode precursormeasured by a scanning electron microscope—an energy-dispersive X-rayspectroscopy (SEM-EDX).

[6] The positive electrode precursor according to [5],

wherein 5≤S₂≤60, and 0.50≤S₂/X≤2.00, when S₂% is an area of oxygen whoseluminance values are binarized based on the average luminance value inthe oxygen mapping obtained by SEM-EDX measurement of the cross sectionof the positive electrode precursor which is processed by a broad ionbeam (BIB).

[7] The positive electrode precursor according to any one of [1] to [6],

wherein 0.3≤D≤5.0 and 0.5≤E≤10 are satisfied, when D (μL/cm²) ismesopore volume per unit area derived from fine pores having a diameterof equal to or larger than 20 Å and equal to or smaller than 500 Å, thediameter of which is calculated by the BJH method at one surface of thepositive electrode precursor, and E (μL/cm²) is micropore volume perunit area derived from fine pores having a diameter of smaller than 20Å, the volume of which is calculated by the MP method.

[8] The positive electrode precursor according to any one of [1] to [7],wherein 0.05≤C/B≤0.5 is satisfied.[9] The positive electrode precursor according to any one of [1] to [8],wherein an average particle diameter of the alkali metal compound isequal to or larger than 0.1 μm and equal to or smaller than 10 μm.[10] A production method for a nonaqueous hybrid capacitor comprisingthe following steps of.(1) a step of accommodating into a casing a laminated body composed ofthe positive electrode precursor according to any one of [1] to [9], anegative electrode containing a negative electrode active material whichis capable of intercalating/releasing lithium ions, and a separator,(2) a step of pouring into the casing a nonaqueous electrolytic solutioncontaining electrolytes including lithium ions, and(3) a step of decomposing the alkali metal compound by applying avoltage between the positive electrode precursor and a negativeelectrode, in this order,wherein A₁/G₁ is equal to or larger than 1.0 (g/Ah) and equal to orsmaller than 2.0 (g/Ah), when A₁ (g/m²) is an amount of the alkali metalcompound per unit area in the positive electrode precursor, G₁ (Ah/m²)is a capacitance per unit area of the negative electrode, and thevoltage which is applied in the step of decomposing the alkali metalcompound is equal to or higher than 4.2 V.[11] The production method for the nonaqueous hybrid capacitor,according to [10], wherein A₁/B₁ is equal to or larger than 0.20 andequal to or smaller than 1.00, when B₁ (g/m²) is a weight per unit areaof the positive electrode active material.[12] The production method for the nonaqueous hybrid capacitor,according to [10] or [11], comprising Lewis acid in an amount of equalto or more than 0.5% by weight and equal to or less than 5% by weight inthe nonaqueous electrolytic solution.[13] The production method for the nonaqueous hybrid capacitor,according to any one of [10] to [12], comprising a crown ether in anamount of equal to or more than 1.0% by weight and equal to or less than10.0% by weight in the nonaqueous electrolytic solution.[14] A nonaqueous hybrid capacitor comprising the positive electrodeprecursor according to any one of [1] to [9].[15] A storage module comprising the nonaqueous hybrid capacitoraccording to [14].[16] A power regeneration system comprising the nonaqueous hybridcapacitor according to [14] or the storage module according to [15].[17] A power load leveling system comprising the nonaqueous hybridcapacitor according to [14] or the storage module according to [15].[18] A non-service interruption power source system comprising thenonaqueous hybrid capacitor according to [14] or the storage moduleaccording to [15].[19] A non-contact electric supply system comprising the nonaqueoushybrid capacitor according to [14] or the storage module according to[15].[20] An energy harvest system comprising the nonaqueous hybrid capacitoraccording to [14] or the storage module according to [15].[21] A power storage system comprising the nonaqueous hybrid capacitoraccording to [14] or the storage module according to [15].

Effects of the Invention

According to the present invention, there can be provided the positiveelectrode precursor for the nonaqueous hybrid capacitor, which iscapable of carrying out pre-doping to the negative electrode in a shorttime by promoting decomposition of the alkali metal compound, andpossessing a high capacitance as well as the production method for thenonaqueous hybrid capacitor which is capable of pre-doping lithium ionsto the negative electrode without using a metal lithium, and having lessgas generation during storage at high temperatures as well as goodcharging and discharging cycle characteristics under a high load.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a drawing showing charging curves at the initial charging ofthe nonaqueous hybrid capacitor obtained in Example 1.

FIG. 2 is a drawing showing charging curves at the initial charging ofthe nonaqueous hybrid capacitor obtained in Comparative Example 1.

FIG. 3 is a drawing showing charging curves at the initial charging ofthe nonaqueous hybrid capacitor obtained in Example 12.

BEST MODE FOR CARRYING OUT THE INVENTION

An explanation on embodiments of the present invention will be givenbelow.

The nonaqueous hybrid capacitor generally has a positive electrode, anegative electrode, a separator, an electrolytic solution, and a casingas main configuration elements. As the electrolytic solution, an organicsolvent dissolved with an electrolyte such as a lithium salt, etc.,(hereafter, it is referred to as the nonaqueous electrolytic solution)is used.

Herein, a positive electrode state before a pre-doping step to bedescribed later is defined as the positive electrode precursor, and apositive electrode state after the pre-doping step is defined as thepositive electrode. The positive electrode precursor in the presentinvention is characterized in comprising a positive electrode activematerial containing a carbon material, and an alkali metal compound. Thepositive electrode precursor in the present invention may be simplycalled with respect to the desired construction of the nonaqueous hybridcapacitor, an electrode before pre-doping, a half-side electrode beforepre-doping, a half cell, a coated electrode, a dried electrode, and etc.

The positive electrode precursor of the present invention is composed ofthe following first and second aspects, and further the productionmethod for the hybrid capacitor using the positive electrode precursoris composed of the third aspect, wherein each aspect may be combinedarbitrarily.

[The First Aspect]

[1] The first aspect in the present invention isthe positive electrode precursor comprising the positive electrodeactive material containing a carbon material, and the alkali metalcompound,

wherein 5≤A≤35, when A (g/m²) is a weight of the alkali metal compoundin the positive electrode active material layer at one surface of thepositive electrode precursor,

10≤B≤100 as well as 0.20≤A/B≤1.00, when B (g/m²) is a weight of thepositive electrode active material in the positive electrode activematerial layer, and

1≤C≤20, when C (m²/cm²) is a specific surface area per unit areameasured by the BET method at one surface of the positive electrodeprecursor.

[The Second Aspect]

[5] The second aspect of the present invention isthe positive electrode precursor,

wherein 5≤X≤50, when X % by weight is a weight ratio of the alkali metalcompound in the positive electrode active material layer of the positiveelectrode precursor,

5≤S₁≤60, and 0.50≤S₁/X≤2.00, when S₁% is an area of oxygen whoseluminance values are binarized based on the average luminance value inthe oxygen mapping of the surface of the positive electrode precursormeasured by a scanning electron microscope—an energy-dispersive X-rayspectroscopy (SEM-EDX).

[The Third Aspect]

[10] The third aspect of the present invention is the production methodfor the nonaqueous hybrid capacitor comprising the following steps of:(1) a step of accommodating into the casing a laminated body composed ofthe positive electrode precursor according to any one of [1] to [9], thenegative electrode containing the negative electrode active materialwhich is capable of intercalating/releasing lithium ions, and aseparator,(2) a step of pouring into the casing the nonaqueous electrolyticsolution containing electrolytes including lithium ions and,(3) a step of decomposing the alkali metal compound by applying avoltage between the positive electrode precursor and the negativeelectrode, in this order,wherein A₁/G₁ is equal to or larger than 1.0 (g/Ah) and equal to orsmaller than 2.0 (g/Ah), when A₁ (g/m²) is an amount of the alkali metalcompound per unit area in the positive electrode precursor, G₁ (Ah/m²)is a capacitance per unit area of the negative electrode, and thevoltage which is applied in the step of decomposing the alkali metalcompound is equal to or higher than 4.2 V.

[Positive Electrode]

The positive electrode has a positive electrode power collector, and apositive electrode active material layer present at one surface or bothsurfaces thereof. The positive electrode is characterized in containingthe alkali metal compound as the positive electrode precursor beforeassembling of a storage element. As will be described later, it ispreferable, in the present invention, that alkali metal ions arepre-doped to the negative electrode in an assembly step of the storageelement, and as the pre-doping method, it is preferable that a voltageis applied between the positive electrode precursor and the negativeelectrode, after assembling of the storage element using the positiveelectrode precursor containing the alkali metal compound, the negativeelectrode, the separator, the casing, and the nonaqueous electrolyticsolution. It is preferable that the alkali metal compound is containedin the positive electrode active material layer formed on the positiveelectrode power collector of the positive electrode precursor.

[Positive Electrode Active Material Layer]

It is preferable that the positive electrode active material layercontains the positive electrode active material including a carbonmaterial, and it may contain, other than this, conductive fillers, abinder, a dispersion stabilizer, etc., as needed.

It is characterized that the alkali metal compound is contained in or atthe surface of the positive electrode active material layer of thepositive electrode precursor.

[Positive Electrode Active Material]

It is preferable that the positive electrode active material containsthe carbon material. It is more preferable to use as this carbonmaterial a carbon nanotube, a conductive polymer, or a porous carbonmaterial, and further preferable to use an activated carbon. As thepositive electrode active material, one or more kinds of materials maybe used by mixing, and materials other than the carbon material (forexample, a composite oxide of lithium and a transition metals, etc.) maybe contained.

It is preferable that a content ratio of the carbon material is equal toor higher than 50% by weight, and more preferably equal to or higherthan 60% by weight with respect to a total amount of the aforementionedpositive electrode active material. A content ratio of the carbonmaterial can be 100% by weight, however, it is preferable to be, forexample, equal to or lower than 95% by weight from the viewpoint ofexhibiting good performance in combination with other materials, and itmay be equal to or lower than 90% by weight. The upper limit and thelower limit of the content ratio of the carbon material may be combinedarbitrarily.

When the activated carbon is used as the positive electrode activematerial, the activated carbon and raw materials thereof are notparticularly restricted. However, it is preferable to control an optimalpore size of the activated carbon in order to satisfy both of high I/Ocharacteristics and high energy density. Specifically, when V₁ (cc/cm²)is mesopore volume obtained from that of fine pores having a diameter ofequal to or larger than 20 Å and equal to or smaller than 500 Å, beingcalculated by the BJH method, and V₂ (cc/cm²) is micropore volumeobtained from that of fine pores having a diameter of smaller than 20 Å,being calculated by the MP method,

(1) the activated carbon satisfying 0.3<V₁≤0.8, 0.5≤V₂≤1.0, and having aspecific surface area measured by the BET method of equal to or largerthan 1,500 m²/g and equal to or smaller than 3,000 m²/g (hereafter it isalso referred to as activated carbon 1) is preferable to exhibit highI/O characteristics, and(2) the activated carbon satisfying 0.8<V₁≤2.5, 0.8<V₂≤3.0, and having aspecific surface area measured by the BET method of equal to or largerthan 2,300 m²/g and equal to or smaller than 4,000 m²/g (hereafter it isalso referred to as activated carbon 2) is preferable to obtain highenergy density.

The BET specific surface area, the mesopore volume, the microporevolume, and an average fine pore diameter of the active material in thepresent invention are values, each of which is determined by thefollowing methods. Measurement of an isothermal line of adsorption anddesorption of the material is carried out by drying a sample undervacuum at 200° C. overnight, and using nitrogen as an adsorbate. Byusing the absorption isotherm obtained here, the BET specific surfacearea is calculated by a BET multi-point method or a BET one-pointmethod, the BJH method and the MP method, respectively.

The BJH method is a calculation method generally used for an analysis ofthe mesopore, and proposed by Barrett, Joyner, Halenda et al.(Non-patent Document 1).

The MP method means a method of determining micropore volume, microporearea and distribution of the micropore, by utilization of “a t-plotmethod” (Non-patent Document 2), and is contrived by R. S. Mikhail,Brunauer, and Bodor (Non-patent Document 3).

In addition, the average fine pore diameter indicates the one determinedby dividing the total fine pore volume per weight of the sample, whichis obtained by measuring each equilibrium adsorption amount of nitrogengas under each relative pressure at liquid nitrogen temperature by theaforementioned BET specific surface area.

It should be noted here that other than a combination of the upper limitvalue of V1 and the lower limit value of V2, a combination of each upperlimit and lower limit is arbitrary.

An explanation on the aforementioned (1) activated carbon 1 and theabove (2) activated carbon 2 will respectively be given below.

(Activated Carbon 1)

Mesopore volume V₁ of activated carbon 1 is preferably larger than 0.3cc/g from the view point of enhancing I/O characteristics, when thepositive electrode material is incorporated into the storage element. Onthe other hand, it is preferably equal to or smaller than 0.8 cc/g fromthe view point of suppressing decrease in bulk density of the positiveelectrode. The aforementioned V₁ is more preferably equal to or largerthan 0.35 cc/g and equal to or smaller than 0.7 cc/g, and furtherpreferably equal to or larger than 0.4 cc/g and equal to or smaller than0.6 cc/g.

Micropore volume V₂ of activated carbon 1 is preferably equal to orlarger than 0.5 cc/g in order to enlarge a specific surface area of theactivated carbon, and to increase a capacitance. On the other hand, itis preferably equal to or smaller than 1.0 cc/g from the view point ofsuppressing bulk density of the activated carbon, and increasing adensity as the electrode and a capacitance per unit volume. Theaforementioned V₂ is more preferably equal to or larger than 0.6 cc/gand equal to or smaller than 1.0 cc/g, and further preferably equal toor larger than 0.8 cc/g and equal to or smaller than 1.0 cc/g.

A ratio, (V₁/V₂) of mesopore volume V₁ with respect to the microporevolume V₂ is preferably in a range of 0.3≤V₁/V₂≤0.9. Accordingly, it ispreferably is equal to or larger than 0.3 from the view point ofenlarging a ratio of the mesopore volume with respect to the microporevolume, whereby a decrease in output characteristics is suppressed, anda high capacitance is held. On the other hand, V₁/V₂ is preferably equalto or smaller than 0.9 from the view point of enlarging a ratio of themicropore volume with respect to the mesopore volume, from which adecrease in a capacitance is suppressed, and high output characteristicshold. The more preferable range of V₁/V₂ is 0.4≤V₁/V₂≤0.7, and thefurther preferable range of V₁/V₂ is 0.55≤V₁/V₂≤0.7.

An average fine pore diameter of activated carbon 1 is preferably equalto or larger than 17 Å, more preferably equal to or larger than 18 Å,and most preferably equal to or larger than 20 Å from the view point ofmaximizing an output of the resulting storage element. The average finepore diameter of activated carbon 1 is also preferably equal to orsmaller than 25 Å from the view point of maximizing a capacitance.

A specific BET surface area of activated carbon 1 is preferably equal toor larger than 1,500 m²/g and equal to or smaller than 3,000 m²/g, andmore preferably equal to or larger than 1,500 m²/g and equal to orsmaller than 2,500 m²/g. When the specific BET surface area is equal toor larger than 1,500 m²/g, a superior energy density is easily obtained.On the other hand, when the specific BET surface area is equal to orsmaller than 3,000 m²/g, performance per electrode volume is high, sincethere is no need to accommodate a large amount of the binder to maintainstrength of the electrode.

Activated carbon 1 having the aforementioned characteristics can beobtained using, for example, the raw materials and the treatment methodsto be explained below.

In the present embodiment, a carbon source used as a raw material ofactivated carbon 1 is not particularly restricted. It includes, forexample, a plant-based raw material such as wood, wood flour, a coconutshell, a byproduct in pulp production, bagasse, waste molasses, andetc.; a fossil-based raw material such as peat, lignite, brown coal,bituminous coal, anthracite, petroleum distilled residues, petroleumpitch, coke, coal tar, and etc.; various kinds of synthetic resins suchas a phenol resin, a vinyl chloride resin, a vinyl acetate resin, amelamine resin, a urea resin, a resorcinol resin, celluloid, an epoxyresin, a polyurethane resin, a polyester resin, a polyamide resin, andetc.; a synthetic rubber such as polybutylene, polybutadiene,polychloroprene, and etc.; other synthetic woods, a synthetic pulp,etc., and carbides thereof. Among these raw materials, the plant-basedmaterial such as the coconut shell, wood powder, and carbides thereofare preferable from the viewpoint of mass productivity and cost, and thecoconut shell carbide is particularly preferable.

As carbonization and activation systems for converting these materialsto activated carbon 1, there can be adopted known methods, for example,a fixed bed system, a moving bed system, a fluid bed system, a slurrysystem, a rotary kiln system, and etc.

A carbonization method of these raw materials includes a calcinationmethod at about 400 to 700° C. (preferably 450 to 600° C.) for about 30minutes to 10 hours using an inert gas such as nitrogen, carbon dioxide,helium, xenon, neon, carbon monoxide, exhaust combustion gas, etc., ormixed gas containing theses inert gases as a main component.

As an activation method for the carbide obtained by the aforementionedcarbonization method, a gas activation method for the calcination usingan activation gas such as steam, carbon dioxide, oxygen, and etc. ispreferably used. Among them, a method for using steam or carbon dioxideas the activation gas is preferable.

In this activation method, it is preferable to activate theaforementioned carbide by taking 3 to 12 hours (preferably 5 to 11hours, and further preferably 6 to 10 hours) by increasing temperatureup to from 800 to 1,000° C., while supplying the activation gas in arate of 0.5 to 3.0 kg/h (preferably 0.7 to 2.0 kg/h).

Furthermore, the aforementioned carbide may be subjected to primaryactivation, in advance, before activation treatment of the carbide. Inthis primary activation, the gas activation method by calcination of thecarbon materials at a temperature of below 900° C., usually usingactivation gas such as steam, carbon dioxide, oxygen, and etc. can bepreferably adopted.

Activated carbon 1 which can be used in the present embodiment, and hasthe aforementioned characteristics can be produced by appropriatecombination of a calcination temperature and calcination time in theaforementioned carbonization method as well as a supplying amount ofactivation gas, an increase rate of the temperature, and the maximumactivation temperature in the aforementioned activation method.

An average particle diameter of activated carbon 1 is preferably 2 to 20μm.

When the average particle diameter is equal to or larger than 2 μm, acapacitance per electrode volume tends to be increased, because thedensity of the active material layer is high. Here, a small averageparticle diameter may induce disadvantage of low durability, however, ithardly occurs when the average particle diameter is equal to or largerthan 2 μm. On the other hand, when the average particle diameter isequal to or smaller than 20 μm, it increases the likelihood of high ratecharging and discharging. The aforementioned average particle diameteris more preferably 2 to 15 μm, and further preferably 3 to 10 μm.

(Activated Carbon 2)

Mesopore volume V₁ of activated carbon 2 is preferably larger than 0.8cc/g from the view point of enhancing output characteristics, when thepositive electrode material is incorporated in the storage element, andon the other hand, it is preferably equal to or smaller than 2.5 cc/gfrom the view point of suppressing a decrease in a capacitance of thestorage element. The aforementioned V₁ is more preferably equal to orlarger than 1.00 cc/g and equal to or smaller than 2.0 cc/g, and furtherpreferably equal to or larger than 1.2 cc/g and equal to or smaller than1.8 cc/g.

On the other hand, micropore volume V₂ of activated carbon 2 ispreferably equal to or larger than 0.8 cc/g to enlarge a specificsurface area of the activated carbon, and to increase a capacitance,while being preferably equal to or smaller than 3.0 cc/g from the viewpoint of increasing a density of an electrode of the activated carbon aswell as a capacitance per unit volume. The aforementioned V₂ is morepreferably equal to or larger than 1.0 cc/g and equal to or smaller than2.5 cc/g, and further preferably equal to or larger than 1.5 cc/g andequal to or smaller than 2.5 cc/g.

Activated carbon 2 having the aforementioned mesopore volume andmicropore volume is the one having the higher BET specific surface areathan that of an activated carbon which has been used for a conventionalelectric double layer capacitor or a lithium ion capacitor. As aspecific value of the BET specific surface area of activated carbon 2 ispreferably equal to or larger than 3,000 m²/g and equal to or smallerthan 4,000 m²/g. It is more preferably equal to or larger than 3,200m²/g and equal to or smaller than 3,800 m²/g. When the BET specificsurface area is equal to or larger than 3,000 m²/g, a superior energydensity is easily obtained, on the other hand, when the BET specificsurface area is equal to or smaller than 4,000 m²/g, performance perelectrode volume is enhanced, since it is not necessary to accommodate alarge amount of the binder to maintain electrode strength.

Activated carbon 2 having aforementioned characteristics can be obtainedby using, for example, the raw materials and the treatment methodsdescribed below.

A carbonaceous material used as a raw material of activated carbon 2 isnot particularly restricted as long as it is a carbon source usuallyused as the raw material of the activated carbon, and includes, forexample, the plant-based raw material such as wood, wood flour, acoconut shell, and etc.; a fossil-based raw material such as petroleumpitch, coke, and etc.; various kinds of synthetic resins such as aphenol resin, a furan resin, a vinyl chloride resin, a vinyl acetateresin, a melamine resin, a urea resin, a resorcinol resin, and etc.Among these raw materials, the phenol resin and the furan resin aresuitable for preparing the activated carbon having a large specificsurface area, and are particularly preferable.

As a carbonization method of these materials or a heating method in theactivation treatment of them, there can be included known methods, forexample, a fixed bed method, a moving bed method, a fluid bed method, aslurry method, a rotary kiln method, and etc. In a heated atmosphere,there can be used an inert gas such as nitrogen, carbon dioxide, helium,argon, etc., or mixed gas containing these gases as a main component.The raw materials are generally calcinized at a carbonizationtemperature from about 400 to 700° C. for about 0.5 to 10 hours.

An activation method of the carbide includes a gas activation method forcalcination using activation gas such as steam, carbon dioxide, oxygen,and etc.; and an alkali metal activation method for carrying out heattreatment after mixing with an alkali metal compound; and the alkalimetal activation method is preferable for preparing an activated carbonhaving a large specific surface area.

In this activation method, heat treatment is carried out under an inertgas atmosphere in a range of 600 to 900° C. for 0.5 to 5 hours aftermixing the carbide and the alkali metal compound such as KOH, NaOH, andetc. so as to adjust a weight ratio of the carbide and the alkali metalcompound to be equal to or larger than 1:1 (the amount of the alkalimetal compound is the same or more than that of the carbide), and thenthe alkali metal compound is removed by washing with an acid and water,followed by drying it.

It is recommendable to mix the carbide with KOH in the activation in aslightly excess amount of the former in order to increase the microporevolume and not to increase the mesopore volume. It is recommendable touse KOH in a slightly excess amount in order to increase both of themicropore volume and the mesopore volume. It is preferable to carry outsteam activation after alkali activation treatment mainly to increasethe mesopore volume.

An average particle diameter of activated carbon 2 is preferably equalto or larger than 2 m and equal to or smaller than 20 μm, and morepreferably equal to or larger than 3 μm and equal to or smaller than 10μm.

(Usage Aspect of Activated Carbon)

Activated carbons 1 and 2 may respectively consist of one kind of anactivated carbon or a mixture of two or more kinds exhibiting theaforementioned each characteristics as the mixture.

As activated carbons 1 and 2, either one or a mixture of them may beselected for use.

The positive electrode active material may contain materials other thanactivated carbons 1 and 2 (for example, an activated carbon not havingspecific V₁ and/or V₂ or a material other than the activated carbons(for example, a composite oxide of lithium and transition metals,etc.)). In the embodiment of the present invention a content ofactivated carbon 1, a content of activated carbon 2, or a total contentof activated carbons 1 and 2 is preferably more than 50% by weight withrespect to a total weight of the positive electrode active material,more preferably more than 70% by weight, further preferably more than90% by weight, and most preferably 100% by weight.

Here, in the first aspect of the present invention, it is preferablethat 5≤A≤35, when A (g/m²) is a weight of the alkali metal compound inthe positive electrode active material layer at one surface of thepositive electrode precursor, 10≤B≤100, and 0.20≤A/B≤1.00, when B (g/m²)is a weight of the positive electrode active material in the positiveelectrode active material layer. Here, a weight of the positiveelectrode active material contained in the positive electrode precursormeans a weight of the material containing, other than the activematerial, arbitrary components such as the conductive fillers, thebinder, the dispersion stabilizers, all of which will be describedlater, and etc.

When A is equal to or larger than 5, a capacitance of a nonaqueoushybrid capacitor increases, since a sufficient amount of the alkalimetal ions is pre-doped to the negative electrode. When A is equal to orsmaller than 35, decomposition of the alkali metal compound is promoteddue to enhancement of electron conduction in the positive electrodeprecursor, therefore pre-doping proceeds efficiently. When B is equal toor larger than 10, an energy density can be increased. When B is equalto or smaller than 100, output characteristics are enhanced, becausediffusion of ions in the positive electrode is accelerated. When A/B isequal to or larger than 0.20, a sufficient amount of the alkali metalions is pre-doped to the negative electrode, thereby the capacitance ofthe nonaqueous hybrid capacitor is increased. When A/B is equal to orsmaller than 1.00, voids generated by decomposition of the alkali metalcompound in the positive electrode precursor after pre-doping becomesmaller, thereby the positive electrode is strengthened.

It should be noted here that any combination of the upper limit value ofA, B or A/B and the lower limit value of A, B or A/B is arbitrary,including the case where all of A, B and A/B are the upper limit valuesor the lower limit values.

(Alkali Metal Compound)

The alkali metal compound in the present invention includes lithiumcarbonate, sodium carbonate, potassium carbonate, rubidium carbonate,cesium carbonate, lithium oxide as well as lithium hydroxide, and one ormore kinds of the alkali metal carbonates is suitable for use, which iscapable of pre-doping by releasing cations which are formed bydecomposition of the compounds in the positive electrode precursor,followed by reduction in the negative electrode. Among them, lithiumcarbonate is suitable for use from the view of having a high capacitanceper unit weight. The alkali metal compound contained in the positiveelectrode precursor may be one kind or two or more kinds of the alkalimetal compounds. Furthermore, the positive electrode precursor of thepresent invention can contain at least one kind of the alkali metalcompound, and may also contain one or more kinds of oxides such as M₂O,hydroxides such as MOH, halides such as MF or MCI, and carboxylate saltssuch as RCOOM (R is H, an alkyl group, and an aryl group), wherein M isone or more kinds selected from Li, Na, K, Rb, and Cs. It may alsocontain one or more kinds of alkaline earth metal carbonates selectedfrom BeCO₃, MgCO₃, CaCO₃, SrCO₃, BaCO₃, alkaline earth metal oxides,alkaline earth metal hydroxides, alkaline earth metal halides, andalkaline earth metal carboxylates.

In the case of containing, other than the alkali metal compound, two ormore kinds of the alkali metal compounds or the alkaline earth metalcompound, it is preferable to prepare the positive electrode precursorso that a total amount of the alkali metal compound and the alkalineearth metal compound contained is equal to or more than 5 g/m² and equalto or less than 35 g/m² in the positive electrode active material layerat one surface of the positive electrode precursor.

In the first aspect of the present invention, the alkali metal compoundis preferably contained in the positive electrode precursor in an amountof equal to or more than 10% by weight, because desirable charging anddischarging cycle characteristics under a high load can be exhibited.Among the alkali metal compounds, lithium carbonate is particularlypreferable.

In the second aspect of the present invention, it is preferable that5≤X≤50, where X (% by weight) is a weight ratio of the alkali metalcompound in the positive electrode active material layer at one surfaceof the positive electrode precursor. X is more preferably 10≤X≤50, andfurther preferably 20≤X≤40. When X is equal to or larger than 5, asufficient amount of the alkali metal ions can be pre-doped to thenegative electrode, thereby a capacitance of the nonaqueous hybridcapacitor increases. When X is equal to or smaller than 50, electronconduction in the positive electrode precursor can be enhanced,therefore decomposition of the alkali metal compound proceedsefficiently.

When the positive electrode precursor contains the aforementioned two ormore kinds of the alkali metal compounds or the alkaline earth metalcompounds, other than the alkali metal compound, the positive electrodeprecursor is preferably prepared, in which a total amount of the alkalimetal compound and the alkaline earth metal compound contained is equalto or larger than 5% by weight and equal to or smaller than 50% byweight in the positive electrode active material layer at one surface ofthe positive electrode precursor.

In the third aspect of the present invention, a content ratio of thealkali metal compound in the positive electrode active material layershould be determined within the aforementioned range by satisfying thespecific values of the ratio of A₁/B₁ (to be described later), where A₁is a weight of the alkali metal compound per unit area in the positiveelectrode precursor, B₁ (g/m²) which is a weight of the positiveelectrode active material, and the ratio of A₁/G₁, where G₁ is acapacitance per unit area in the negative electrode.

—Charging and Discharging Cycle Characteristics Under High Load—

In charging and discharging the nonaqueous hybrid capacitor, alkalimetal ions and anions in an electrolytic solution move accompanied bycharging and discharging, and react with the active material. Activationenergy of an insertion reaction of ions into the active material andthat of a desorption reaction are different from each other.Accordingly, when charging or discharging loads are particularly large,the ions cannot follow the change of the charging or discharging,thereby some ions cannot move, and thus are accumulated in the activematerial. As a result, the concentration of electrolytes in a bulkelectrolytic solution decreases, from which the resistance of thenonaqueous hybrid capacitor increases.

However, when the alkali metal compound is contained in the positiveelectrode precursor, by oxidative decomposition of the alkali metalcompound, the alkali metal ions are released for pre-doping to thenegative electrode, while voids capable of holding the electrolyticsolution inside the positive electrode are formed. It is considered thatthe ions are supplied to the positive electrode at any time from theelectrolyte held in such voids which are formed in the vicinity of theactive material during charging and discharging, from which charging anddischarging cycle characteristics under a high load are enhanced.

The alkali metal compound contained in the positive electrode precursorreleases the alkali metal ions by oxidative decomposition under a highvoltage which is applied, when the nonaqueous hybrid capacitor isformed, and the pre-doping proceeds by reduction of the ions at thenegative electrode. Therefore, the pre-doping step can be shortened byaccelerating the oxidation reaction. In order to promote the reductionreaction, it is important to ensure electron conduction by contactingthe alkali metal compound (an insulating material) with the positiveelectrode active material, and to diffuse the cations released by theoxidation reaction into the electrolytic solution. Thus, it is ofimportance to cover in a moderate manner the surface of the positiveelectrode active material with the alkali metal compound.

In the second aspect of the present invention, oxidative decompositionof the alkali metal compound is accelerated when 5≤S₁≤60, and0.50≤S₁/X≤2.00 are satisfied, where S₁% is an area of oxygen whoseluminance values are binarized based on the average luminance value inthe oxygen mapping of the surface of the positive electrode precursormeasured by a scanning electron microscope—an energy-dispersive X-rayspectroscopy (SEM-EDX). When S₁ is equal to or larger than 5%,pre-doping is accelerated, since electron conduction between the alkalimetal compound and the positive electrode active material is ensured.When S₁ is equal to or less than 60%, pre-doping is accelerated, becausediffusion of the alkali metal ions in the electrolytic solution ispromoted. When S₁/X is equal to or larger than 0.50, pre-doping isaccelerated, because diffusion of the electrolytic solution in thepositive electrode precursor is promoted. When S₁/X is equal to orsmaller than 2.00, pre-doping is accelerated, because electronconduction between the alkali metal compound and the positive electrodeactive material is ensured.

In the second aspect, it is also preferable that 5≤S₂≤60, and0.50≤S₂/X≤2.00, where S₂(%) denotes an area of oxygen whose luminancevalues are binarized based on the average value of luminance values ofoxygen in the oxygen mapping by SEM-EDX of the cross section of thepositive precursor which was processed by a broad ion beam (BIB). WhenS₂ is equal to or larger than 5%, electron conduction between the alkalimetal compound and the positive electrode active material is secured,and pre-doping is accelerated. When S₂ is equal to or smaller than 60%,diffusion of the alkali metal ions in the electrolytic solution ispromoted, and therefore the pre-doping is accelerated. When S₂/X isequal to or larger than 0.5, diffusion of the electrolytic solution inthe positive electrode precursor is promoted, and then the pre-doping isaccelerated. When S₂/X is equal to or smaller than 2.00, electronconduction between the alkali metal compound and the positive electrodeactive material is secured, thereby the pre-doping is accelerated.

As a measurement method for S₁ and S₂, they are determined as an area ofoxygen at the surface of the positive electrode precursor and thecross-section of the positive electrode precursor, where luminancevalues of oxygen are binarized based on the average value of luminancevalue in the element mapping measured by SEM-EDX. As a method forforming the cross-section of the positive electrode precursor, the BIBprocessing method can be applied in which argon beams are irradiatedfrom the upper part of the positive electrode precursor, followed bypreparation of a smooth cross-section along with an end part of ashielding plate installed right above the sample.

Measurement conditions of an element mapping of SEM-EDX are notparticularly restricted, and pixel numbers are in a range of 128×128pixels to 512×512 pixels, brightness and contrast are adjusted so thatthere are no pixels exhibiting the maximum brightness value in a mappingimage, and an average value of brightness ones falls within a range of40% to 60% of the maximum brightness value.

Various methods can be used for atomization of the alkali metal compoundand the alkaline earth metal compound. A grinding machine, for example,a ball mill, a beads mill, a ring mill, a jet mill, a rod mill, etc. canbe used.

Alkali metal elements and alkaline earth metal elements can bequantified by using ICP-AES, atomic absorption spectrometry, afluorescent X-ray analysis method, a neutron radio activation analysismethod, ICP-MS, and etc.

In the first and the second aspects of the present invention, an averageparticle diameter of the alkali metal compound is preferably equal to orlarger than 0.1 μm and equal to or smaller than 10 μm. When it is equalto or larger than 0.1 μm, the positive electrode precursor becomessuperior in dispersibility thereof. When it is equal to or smaller than10 μm, a surface area of the alkali metal compound increases, and thendecomposition reaction proceeds efficiently.

A measurement method of an average particle diameter of the alkali metalcompound in the positive electrode precursor is not particularlyrestricted, and can be carried out by calculation from a SEM image and aSEM-EDX image of the cross-section of the positive electrode. As amethod for forming a cross-section of the positive electrode, a BIBprocessing method can be applied in which argon beams are irradiatedfrom an upper part of the positive electrode, followed by preparing asmooth cross-section along with an end part of the shielding plateinstalled right above the sample.

[Discrimination Method of Alkali Metal Compound and Positive ElectrodeActive Material]

The alkali metal compound and the positive electrode active material canbe discriminated in oxygen mapping using a SEM-EDX image of thecross-section of the positive electrode observed at a magnification of1000 times to 4000 times. As for the measurement method of the SEM-EDXimage, it is preferable that brightness and contrast are adjusted sothat there are no pixels exhibiting the maximum brightness value in amapping image, and an average value of brightness values falls within arange of 40% to 60% of the maximum brightness value. Particles having abright part obtained by binarization based on the average value of theluminance values in the oxygen mapping, and occupying the area of equalto or larger than 50% can be discriminated as the alkali metal compound.

[Calculation Method of Average Particle Diameter]

The average particle diameter of the alkali metal compound can bedetermined by analysis of an image of the cross-section of the positiveelectrode obtained by SEM-EDX measurement which was observed, andmeasured in the same view field as that of the aforementioned SEMcross-section of the positive electrode. A cross-sectional area T isdetermined on basis of the whole particles of the alkali metal compoundwhich are discriminated from the aforementioned SEM image of thecross-section of the positive electrode, and a particle diameter d iscalculated by the following equation (1) (circular constant isrepresented by 7):

[Equation 1]

d=2×(T/π)^(1/2)  (1)

A volume average particle diameter Z₀ is determined by the followingequation (2) using the resulting particle diameter d:

[Equation 2]

X ₀=Σ[4/3π×(d/2)³ ×d]/Σ[4/3π×(d/2)³]  (2)

The average particle diameter of the alkali metal compound can becalculated by the average value of Z₀ values which are calculated bychanging a view field of the cross-section of the positive electrode,and measuring these values at five fields and more.

(Other Components of Positive Electrode Active Material Layer)

The positive electrode active material layer of the positive electrodeprecursor in the present invention may contain arbitrary components asnecessary such as the conductive fillers, the binder, the dispersionstabilizer, and etc., other than the positive electrode active materialand the alkali metal compound.

As the aforementioned conductive filler, a conductive carbonaceousmaterial having higher conductivity than that of the positive electrodeactive material can be included. For example, Ketjen black, acetyleneblack, a vapor-grown carbon fiber, graphite, a carbon nanotube, amixture thereof, and etc. are preferable for such conductive fillers.

A Mixed amount of the conductive fillers in the positive electrodeactive material layer of the positive electrode precursor is preferably0 to 20 parts by weight, and more preferably in a range of 1 to 15 partsby weight with respective to 100 parts by weight of the positiveelectrode active material. It is preferable to mix the conductivefillers from a high input point of view. However, it is not preferableto mix in an amount exceeding 20 parts by weight, because the contentratio of the positive electrode active material in the positiveelectrode active material layer decreases, and thus the energy densityper volume of the positive electrode active material layer decreases.

The binder is not particularly restricted, and there can be used, forexample, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene),polyimide, a latex, a styrene-butadiene copolymer, a fluorocarbonrubber, an acrylic copolymer, and etc. An amount of the binder used ispreferably equal to or more than 1 part by weight and equal to or lessthan 30 parts by weight, more preferably equal to or more than 3 partsby weight and equal to or less than 27 parts by weight, and furtherpreferably equal to or more than 5 parts by weight and equal to or lessthan 25 parts by weight with respect to 100 parts by weight of thepositive electrode active material. When the amount of the binder isequal to or more than 1% by weight, the material exhibits sufficientelectrode strength. On the other hand, when the amount of the binder isequal to or less than 30 parts by weight, entry of ions into thepositive electrode active material and exit of ions from the material aswell as diffusion of the ions are not hindered, thereby high I/Ocharacteristics are exhibited.

The dispersion stabilizer is not particularly restricted, and there canbe used, for example, PVP (polyvinyl pyrrolidone), PVA (polyvinylalcohol), a cellulose derivative, and etc. An amount of the binder usedis preferably equal to or more than 0 part by weight and equal to orless than 10 parts by weight with respect to 100 parts by weight of thepositive electrode active material. When the amount of the dispersionstabilizer is equal to or less than 10 parts by weight, no entry of ionsinto the positive electrode active material and no exit of ions from thematerial as well as no diffusion of the ions are hindered, thereby highI/O characteristics are exhibited.

[Positive Electrode Power Collector]

A material composing the positive electrode power collector in thepresent invention is not particularly restricted as long as it has highelectron conductivity, and does not induce deterioration caused byelution to the electrolytic solution as well as reactions with theelectrolytes or ions, etc., and thus a metal foil is preferable. As thepositive electrode power collector in nonaqueous hybrid capacitor of thepresent embodiment, an aluminum foil is particularly preferable.

The metal foil may be a conventional metal foil without a surface withruggedness or through holes, a metal foil having a surface withruggedness, being subjected to emboss finish, chemical etching, anelectro-deposition method, blast finish, and etc., or a metal foilhaving through holes such as an expand metal, a punching metal, anetching foil, and etc.

A thickness of the positive electrode power collector is notparticularly restricted as long as the shape and strength of thepositive electrode sufficiently hold, and it is preferable, for example,from 1 to 100 μm.

[Production of Positive Electrode Precursor]

In the present invention, the positive electrode precursor, which isconverted to the positive electrode of the nonaqueous hybrid capacitorcan be produced by production technologies for electrodes of knownlithium ion batteries, electric double layer capacitors, and etc. Forexample, the positive electrode precursor can be prepared using aslurry-like coating solution by dispersing or dissolving the positiveelectrode active material and the alkali metal compound as well as otherarbitrary components used as needed into water or an organic solvent,coating this coating solution onto one surface or both surfaces of thepositive electrode power collector to form a coated film, and thusdrying them. Furthermore, film thickness or the bulk density of thepositive electrode active material layer may be adjusted by applyingpressure to the resulting positive electrode precursor. Alternatively,the following method of mixing in a dried atmosphere the positiveelectrode active material and the alkali metal compound as well as otherarbitrary components used as needed without a solvent, press-molding theresulting mixture, and then attaching it to the positive electrode powercollector by using conductive adhesives, may also applied.

A coating solution of the aforementioned positive electrode precursormay be prepared by dry-blending a part of or all of various kinds powdermaterials containing the positive electrode active material, followed byaddition of water or an organic solvent, and/or a liquid or slurrymaterial, in which the binder or the dispersing agent is dissolved ordispersed. It may be prepared by addition of various kinds of the powdermaterials containing the positive electrode active material in theliquid or slurry material, in which the binder or the dispersionstabilizer is dissolved or dispersed. It may be prepared by addition ofvarious kinds of powder materials containing the positive electrodeactive material into the liquid or slurry material, in which the binderor the dispersing agent is dissolved or dispersed in water or an organicsolvent. As the dry-blending method, the conductive material may also becoated onto the alkali metal compound having low conductivity bypre-mixing the positive electrode active material and the alkali metalcompound as well as the conductive fillers as needed using for example,a ball mill, etc. In this way, the alkali metal compound has a highlikelihood of decomposition easily at the positive electrode precursorin the pre-doping step. When water is used as a solvent of the coatingsolution, the coating solution may exhibit alkaline by addition of thealkali metal compound, thereby a pH modifier may be added as needed tothe coating solution.

Although preparation of the coating solution of the aforementionedpositive electrode precursor is not particularly restricted, adispersing machine such as a homo-disperser or a multi-axis dispersingmachine, a planetary mixer, a thin film spin-type high speed mixer, andetc. are suitable for use. It is preferable to carry out dispersionunder the condition of a peripheral speed of equal to or faster than 1m/sec and equal to or slower than 50 m/sec to obtain a coating solutionin a well dispersed state. When the peripheral speed is equal to orfaster than 1 m/sec, it is preferable, various kinds of materials arepreferably dissolved or dispersed in a well dispersed state. When theperipheral speed is equal to or slower than 50 m/sec, various kinds ofmaterials are not fractured by heat or shear force due to dispersion,and no re-aggregation of the materials occurs.

Dispersity of the aforementioned coating solution is preferably equal toor larger than 0.1 μm and equal to or smaller than 100 μm which aremeasured by a particle gauge. The upper limit of the degree, theparticle size is more preferably equal to or smaller than 80 μm, andfurther preferably equal to or smaller than 50 μm. When the particlesize is equal to or smaller than 0.1 μm, that means the size is equal toor smaller than the size of various kinds of powder materials containingthe positive electrode active material, therefore the materials is in astate of being unpreferably crushed when preparing the coating solution.When the particle size is equal to or smaller than 100 μm, stablecoating can be conducted without clogging in supplying the coatingsolution or generation of stripes of the coated film, etc.

Viscosity (ηb) of the coating solution of the aforementioned positiveelectrode precursor is preferably equal to or higher than 1,000 mPa·sand equal to or lower than 20,000 mPa·s. It is more preferably equal toor higher than 1,500 mPa·s and equal to or lower than 10,000 mPa·s, andfurther preferably equal to or higher than 1,700 mPa·s and equal to orlower than 5,000 mPa·s. When viscosity (ηb) is equal to or higher than1,000 mPa·s, dripping is suppressed in the case of forming a coatedfilm, and thus width and thickness of the coated film can be controlledas desired. When viscosity is equal to or lower than 20,000 mPa·s,stable coating can be carried out because a pressure loss which occursby using a coating machine is low at a flow passage of the coatingsolution, thereby the coated film thickness can be controlled to equalto or less than desired thickness.

The value, TI (thixotropy index value) of the coating solution ispreferably equal to or higher than 1.1. It is more preferably equal toor higher than 1.2, and further preferably equal to or higher than 1.5.When TI is equal to or higher than 1.1, width and thickness of thecoated film can be controlled as desired.

A method for forming a coating film of the positive electrode precursoris not particularly restricted, and a coating machine such as a diecoater or a comma coater, a knife coater, a gravure coating machine, andetc. can preferably be used. The coating film may be formed bysingle-layer coating or by multi-layer coating. In the case of themulti-layer coating, the composition of the coating solution may beadjusted so that the content of the alkali metal compound in each of thecoated film layer is different. A coating speed is preferably equal toor faster than 0.1 m/min and equal to or slower than 100 m/min. It ismore preferably equal to or faster than 0.5 m/min and equal to or slowerthan 70 m/min, and further preferably equal to or faster than 1 m/minand equal to or slower than 50 m/min. When a coating speed is equal toor faster than 0.1 m/min, stable coating can be carried out. On theother hand, when the coating speed is equal to or slower than 100 m/min,coating accuracy is secured.

In the third aspect of the present invention, it is preferable thatA₁/B₁ is equal to or larger than 0.20 and equal to or smaller than 1.00,where A₁ (g/m²) is a weight of the alkali metal compound per unit areain the aforementioned positive electrode precursor formed, and B (g/m²)is weight per unit area of the positive electrode active material in thepositive electrode precursor. Accordingly, when preparing theaforementioned slurry, the amount of the alkali metal compound to bemixed with the positive electrode materials (the positive electrodeactive material, the conductive fillers, and the binder, as needed) inpreparing the slurry is preferably adjusted so that A_(1a)/B_(1a)becomes equal to or larger than 0.20 and equal to or smaller than 1.00,where A_(1a) (g) is a weight of the alkali metal compound, and B_(1a)(g) is a weight of the positive electrode materials (a total weight ofthe positive electrode active material, the conductive fillers, and thebinder).

When A₁/B₁ is equal to or larger than 0.20, a sufficient amount of thealkali metal ions can be pre-doped to the negative electrode. When A₁/B₁is equal to or smaller than 1.00, a positive electrode density after areaction of the alkali metal compound can be increased, and thusstrength of the positive electrode holds.

A drying method of the coating film of the aforementioned positiveelectrode precursor is not particularly restricted, and a method such ashot air drying or infrared ray (IR) drying, and etc. is suitable foruse. Drying of the coating film may be carried out at single temperatureor by changing temperatures in multi-stages. It may be dried by acombination of several drying methods. A drying temperature ispreferably equal to or higher than 25° C. and equal to or lower than200° C. It is more preferably equal to or higher than 40° C. and equalto or lower than 180° C., and further preferably equal to or higher than50° C. and equal to or lower than 160° C. When the drying temperature isequal to or higher than 25° C., a solvent in the coated film can besufficiently volatilized. On the other hand, when the drying temperatureis equal to or lower than 200° C., cracking of the coated film caused byabrupt volatilization of the solvent, localization of the binder causedby migration, and oxidation of the positive electrode power collector orthe positive electrode active material layer can be suppressed.

A pressing method of the aforementioned positive electrode precursor isnot particularly restricted, and a pressing machine such as a hydraulicmachine, a vacuum press machine, and etc. is suitable for use. A filmthickness, a bulk density of the positive electrode active materiallayer, and electrode strength can be adjusted by pressing pressure, agap between press rolls, and a surface temperature of the pressing partdescribed later. The pressing pressure is preferably equal to or higherthan 0.5 kN/cm and equal to or lower than 20 kN/cm. It is morepreferably equal to or higher than 1 kN/cm and equal to or lower than 10kN/cm, and further preferably equal to or higher than 2 kN/cm and equalto or lower than 7 kN/cm. When the pressing pressure is equal to orhigher than 0.5 kN/cm, the electrode strength can be increasedsufficiently. On the other hand, when the pressing pressure is equal toor lower than 20 kN/cm, the film thickness or the bulk density of thepositive electrode active material layer can be adjusted to a desiredlevel, without generating warpage or wrinkle in the positive electrodeprecursor. A gap between the press rolls can be set to an arbitraryvalue in accordance to the film thickness of the positive electrodeprecursor after drying so as to obtain the desired film thickness or thebulk density of the positive electrode active material layer. Further, apressing speed may be set to arbitrary level where no warpage or wrinklein the positive electrode precursor is generated. A surface temperatureof the pressing part may be room temperature, or it may be heated asneeded. The lower limit of surface temperature of the press part whenheated is preferably equal to or higher than melting point minus 60° C.of the binder to be used, more preferably equal to or higher thanmelting point minus 45° C. of the binder, and further preferably equalto or higher than melting point minus 30° C. of the binder. On the otherhand, the upper limit of surface temperature of the pressing part whenheated is preferably equal to or lower than melting point plus 50° C. ofthe binder to be used, more preferably equal to or lower than meltingpoint plus 30° C. of the binder, and further preferably equal to orlower than melting point plus 20° C. of the binder. For example, whenPVdF (polyvinylidene fluoride: melting point 150° C.) is used as thebinder, it is preferably heated to equal to or higher than 90° C. andequal to or lower than 200° C. It is more preferably heated to equal toor higher than 105° C. and equal to or lower than 180° C., and furtherpreferably equal to or higher than 120° C. and equal to or lower than170° C. When a styrene-butadiene copolymer (melting point 100° C.) isused as the binder, it is preferably heated to equal to or higher than40° C. and equal to or lower than 150° C. It is more preferably heatedto equal to or higher than 55° C. and equal to or lower than 130° C.,and further preferably equal to or higher than 70° C. and equal to orlower than 120° C.

A melting point of the binder can be determined by an endothermic peakposition of DSC (Differential Scanning Calorimetry). For example, byusing a Differential Scanning Calorimeter “DSC7”, manufactured by PerkinElmer Co., Ltd., the endothermic peak temperature in a temperatureincreasing process provides the melting point, when setting 100 g of asample resin into a measurement cell, and increasing temperature from30° C. to 250° C. at a temperature increasing rate of 10° C./min. undera nitrogen gas atmosphere.

The pressing may be carried out several times by changing conditions ofthe pressing pressure, the gap, the speed, and the surface temperatureof the pressing part.

A thickness of the positive electrode active material layer ispreferably equal to or more than 20 μm and equal to or less than 200 μmat one surface of the positive electrode power collector. The thicknessof the positive electrode active material layer is more preferably equalto or more than 25 μm and equal to or less than 100 μm at one surface,and further preferably equal to or more than 30 μm and equal to or lessthan 80 μm at one surface. When this thickness is equal to or more than20 μm, sufficient charging and discharging capacitances can beexhibited. On the other hand, when this thickness is equal to or lessthan 200 μm, ion diffusion resistance inside the electrode can bemaintained low. Therefore, sufficient output characteristics can beensured as well as cell volume can be reduced, leading to an increase inan energy density. The thickness of the positive electrode activematerial layer, in the case where the power collector has through hallsor a surface with ruggedness, means the average value of thickness atone surface of a part of the layer not having the through halls or thesurface with ruggedness of the power collector.

The pore volume, the micropore volume, and the average fine porediameter in the positive electrode precursor of the present inventionare determined by the following methods: Measurement of an isothermal ofadsorption and desorption is carried out using nitrogen as an adsorbateby vacuum-drying the positive electrode precursor at 200° C. overnight.Then, by using the resulting desorption isotherm, a BET specific surfacearea is calculated by a BET multi-point method or a BET one-pointmethod, a mesopore by the BJH method, and a micropore by the MP method,respectively. By dividing each of the resulting BET specific surfacearea, the mesopore volume, the mesopore volume with an area of thepositive electrode precursor, the BET specific surface area per unitarea C (m²/cm²), the mesopore volume per unit area D (μL/cm²), and themesopore volume per unit area E (μL/cm²) can be calculated.

The BJH method is a calculation method generally used in analysis of themesopore proposed by Barrett, Joyner, Halenda et al. (Non-patentDocument 1).

The MP method means a method of determining micropore volume, amicropore area, and distribution of the micropore by utilization of “at-plot method” (Non-patent Document 2), and is a method contrived by R.S. Mikhail, Brunauer, and Bodor (Non-patent Document 3).

The average fine pore diameter is the one determined by dividing totalfine pore volume per weight of a sample which is obtained by measuringeach equilibrium adsorption amount of nitrogen gas at liquid nitrogentemperature under the corresponding each relative pressure by the BETspecific surface area.

In the first aspect of the present invention, it is preferable that aBET specific surface area at unit area, C is equal to or larger than 1and equal to or smaller than 20, and a ratio of C/B is preferably equalto or larger than 0.05 and equal to or smaller than 0.5, where B (g/m²)is a weight of the positive electrode active material in the positiveelectrode active material layer in the positive electrode precursor.When the ratio of C/B is equal to or larger than 0.05, a reaction of thealkali metal compound is accelerated, since the nonaqueous electrolyticsolution can be impregnated sufficiently in the positive electrodeprecursor, thereby a pre-doping step can be completed in a short period.When the ratio of C/B is equal to or smaller than 0.5, reactionovervoltage of the alkali metal compound can be lowered, since a contactarea between the positive electrode active material and the alkali metalcompound increases.

In the second aspect of the present invention, it is preferable thatmesopore volume per unit area, D is equal to or larger than 0.3 andequal to or smaller than 5.0. When the volume, D is equal to or largerthan 0.3, superior output characteristics are obtained. When the volume,D is equal to or smaller than 5.0, a bulk density of the positiveelectrode precursor can be increased.

Further, in the second aspect, it is preferable that micropore volumeper unit area, E is equal to or larger than 0.5 and equal to or smallerthan 10. When the volume, E is equal to or larger than 0.5, an energydensity can be increased. When the volume, E is equal to or smaller than10, the bulk density of the positive electrode precursor can beincreased.

Dispersity in the present invention is determined by a dispersityevaluation test using a particle gauge specified in JIS K5600. Here, ina particle gauge having a groove with desired depth which fits to aparticle size, a sufficient amount of a sample is poured into the tip ofa deeper side of the groove, and then is overflown a little from thegroove. Next, a blade tip is placed so as to contact with the deeper tipof the groove of the particle gauge where a longer side of the scraperis placed in parallel to width direction of the gauge, and the scraper,being kept in a state it touches the surface of the gauge, is drawntoward the direction of the right angle to the longer side direction ofthe groove until it reaches to 0 depth of the groove at the uniformspeed within 1 or 2 seconds. After completion of the drawing, byirradiating light to the observed area in an angle of equal to or largerthan 20 degree and equal to or smaller than 30 degree within 3 seconds,the depth of the particles which appear at the groove of the particlegauge was measured.

Viscosity (ηb) and the value of TI in the present invention aredetermined respectively by each of the following methods. Firstly, byusing an E-type viscometer, stabilized viscosity (ηa) is measured afterit has been measured for equal to or longer than 2 minutes under thecondition of a temperature of 25° C. and a shear rate of 2 s⁻¹, followedby determination of viscosity (ηb) which is measured under the sameconditions as before except for changing the shear rate to 20 s⁻¹. TI iscalculated by the equation TI=ηa/ηb using the viscosity values obtainedabove. In the case of increasing the shear rate from 2 s⁻¹ to 20 s⁻¹, itmay be increased by one step or in multiple steps within the aboverange, where the viscosity with respect to the shear rate in each stepis determined.

<Negative Electrode>

The negative electrode has a negative electrode power collector and anegative electrode active material layer present at one surface or bothsurfaces thereof.

[Negative Electrode Active Material Layer]

The negative electrode active material layer contains a negativeelectrode active material which is capable of intercalating andreleasing the alkali metal ions. It may contain arbitrary componentssuch as the conductive fillers, the binder, the dispersion stabilizer,and etc. as needed, other than the materials.

[Negative Electrode Active Material]

The aforementioned negative electrode active material, a material whichis capable of intercalating/releasing the alkali metal ions.Specifically, a carbon material, titanium oxide, silicon, silicon oxide,a silicon alloy, a silicon compound, tin, a tin compound, and etc. areexemplified. The content ratio of the carbon material is preferablyequal to or larger than 50% by weight, and more preferably equal to orlarger than 70% by weight with respect to the total amount of thenegative electrode active material. The content ratio of the carbonmaterial may be 100% by weight, however, it is preferable to be equal toor smaller than 90% by weight from the view point of obtaining adesirable effect of combined use of other materials. It may also beequal to or less than 80% by weight. The upper limit and the lower limitof the content ratio of the carbon materials may be combined arbitrarilyin these ranges.

As the aforementioned carbon material, there can be included, forexample, a hard carbon material; a soft carbon material; carbon black;carbon nanoparticles; an activated carbon; artificial graphite; naturalgraphite; graphitized mesophase carbon microspheres; graphite whiskers;an amorphous carbonaceous material such as a polyacene-based material; acarbonaceous material obtained by heat treatment of a carbon precursorsuch as a petroleum-based pitch, a coal-based pitch, mesocarbonmicrobeads, coke, and synthetic resins (for example, a phenol resin,etc.); a thermal decomposition product of a furfuryl alcohol resin or anovolac resin; fullerene; a carbon nanohom; and composite carbonmaterials thereof.

It is preferable that the BET specific surface area of the compositecarbon material is equal to or larger than 100 m²/g and equal to orsmaller than 350 m²/g. This BET specific surface area is preferablyequal to or larger than 150 m²/g and equal to or smaller than 300 m²/g.When the BET specific surface area is equal to or larger than 100 m²/g,the negative electrode active material layer can be made thinner,because a pre-doping amount of the alkali metal ions can be increasedsufficiently. When the BET specific surface area is equal to or smallerthan 350 m²/g, the negative electrode active material layer exhibitssuperior coating property.

For the aforementioned composite carbon material, when carrying outcharging at a measurement temperature of 25° C. using lithium metal as acounter electrode under the constant current of 0.5 mA/cm² up to thevoltage value of 0.01 V, followed by charging under the constant voltagedown to the current value of 0.01 mA/cm², the initial chargingcapacitance is preferably equal to or larger than 300 mAh/g and equal toor smaller than 1,600 mAh/g per unit weight of the composite carbonmaterial. It is more preferably equal to or larger than 400 mAh/g andequal to or smaller than 1,500 mAh/g, and further preferably equal to orlarger than 500 mAh/g and equal to or smaller than 1,450 mAh/g. When theinitial charging capacitance is equal to or larger than 300 mAh/g, apre-doping amount of the alkali metal ions can be sufficientlyincreased, thereby, even when the negative electrode active materiallayer is made thinner, high output characteristics can be obtained. Whenthe initial charging capacitance is equal to or smaller than 1,600mAh/g, swelling and shrinkage of the composite carbon material in dopingand de-doping of the alkali metal ions to the composite carbon materialcan be decreased, thereby strength of the negative electrode holds.

It is particularly preferable that the negative electrode activematerial described above is a composite porous material satisfying thefollowing conditions (1) and (2) from the view point of obtaining anexcellent internal resistance value.

(1) The mesopore volume, Vm₁(cc/g) (volume of fine pores having adiameter of equal to or larger than 2 nm and equal to or smaller than 50nm) calculated by the BJH method satisfies the condition of0.01≤Vm₁<0.10.(2) The micropore volume, Vm₂(cc/g)(volume of fine pores having adiameter of below 2 nm) calculated by the BJH method satisfies thecondition of 0.01≤Vm₂≤0.30.

It is preferable that the negative electrode active material is in aparticulate fashion.

Particle diameters of the silicon and the silicon compound as well astin and the tin compound are preferably equal to or larger than 0.1 μmand equal to or smaller than 30 μm. When the particle diameter is equalto or larger than 0.1 μm, resistance of the nonaqueous hybrid capacitorcan be lowered, since a contact area with the electrolytic solutionincreases. When the particle diameter is equal to or smaller than 30 μm,swelling and shrinkage of the negative electrode are decreased, which iscaused by doping and de-doping of the alkali metal ions to the negativeelectrode which are accompanied by charging and discharging, therebystrength of the negative electrode holds.

The silicon, the silicon compound, and the tin as well as the tincompound can be atomized by crushing using a built-in jet mill in aclassifier, a stirring-type ball mill, and etc. The crushing machine isequipped with a centrifugal classifier, and is capable of capturing fineparticles using a cyclone or a dust collector under inert atmosphere ofan inert gas such as nitrogen, argon, and etc.

A content ratio of the negative electrode active material in thenegative electrode active material layer of the negative electrode ispreferably equal to or larger than 70% by weight, and more preferablyequal to or larger than 80% by weight based on a total weight of thenegative electrode active material layer.

(Other Components of Negative Electrode Active Material Layer)

The negative electrode active material layer in the present inventionmay contain arbitrary components such as conductive fillers, the binder,the dispersion stabilizer, and etc. as needed, other than the negativeelectrode active material.

As the binder, for example, polyvinylidene fluoride (PVdF),polytetrafluoroethylene (PTFE), fluorocarbon rubber, latex, an acrylpolymer, and etc. can be used. An amount of the binder used in thenegative electrode active material layer is preferably 3 to 25 parts byweight, and further preferably a range of 5 to 20 parts by weight withrespect to 100 parts by weight of the negative electrode activematerial. When the amount of the binder is below 3 parts by weight,sufficient adhesion strength cannot be secured between the powercollector and the negative electrode active material layer in thenegative electrode (precursor), thereby interfacial resistance betweenthe power collector and the active material layer increases. On theother hand, when the amount of the binder used is larger than 25 partsby weight, the binder excessively covers the surface of the activematerial of the negative electrode (precursor), and thereby diffusionresistance of ions inside the fine pores of the active materialincreases.

It is preferable that the conductive fillers are composed of aconductive carbonaceous material having higher conductivity than that ofthe negative electrode active material. As such conductive fillers, forexample, ketjen black, acetylene black, a vapor-phase growth carbonfiber, graphite, a carbon nanotube, a mixture thereof, and etc. arepreferable.

A mixing amount of the conductive fillers in the negative electrodeactive material layer is preferably equal to or less than 20 parts byweight, and further preferably in a range of 1 to 15 parts by weightwith respect to 100 parts by weight of the negative electrode activematerial. The conductive fillers are preferably mixed from the viewpoint of a high input, however, when the mixing amount of the fillersbecomes more than 20 parts by weight, the content of the negativeelectrode active material in the negative electrode active materiallayer decreases, thereby the energy density per unit volume unfavorablydecreases.

[Negative Electrode Power Collector]

A material for composing the negative electrode power collector in thepresent invention is preferably a metal foil having high electronconductivity and the one in which no elution to an electrolytic solutionas well as no deterioration of the material due to the reaction with theelectrolytes, ions, or etc. takes place. The aforementioned metal foilis not particularly restricted, and includes, for example, an aluminumfoil, a copper foil, a nickel foil, a stainless steel foil, and etc. Asthe negative electrode power collector in the nonaqueous hybridcapacitor of the present embodiment, the copper foil is preferable.

The metal foil may be a usual metal foil not having a surface withruggedness or through holes, or a metal foil having a surface withruggedness which was formed by emboss finish, chemical etching, anelectro-deposition method, blast finish, and etc. It may also be a metalfoil having through holes such as an expand metal, a punching metal, anetching foil, and etc.

A thickness of the negative electrode power collector is notparticularly restricted as long as shape and strength of the negativeelectrode hold. The preferable thickness, for example, is in a range of1 to 100 μm.

[Production of Negative Electrode]

The negative electrode is composed of the negative electrode activematerial layer at one surface or both surfaces of the negative electrodepower collector. In a typical aspect, the negative electrode activematerial layer is firmly adhered to the negative electrode powercollector.

The negative electrode can be produced by utilizing the productiontechnologies of the electrode for known lithium ion batteries, theelectric double layer capacitor, and etc. For example, the negativeelectrode can be obtained by preparing a slurry coating solution inwhich various kinds of materials containing the negative electrodeactive material are dispersed or dissolved into water or an organicsolvent, coating this coating solution onto one surface or both surfacesof the negative electrode power collector to form a coated film, andthen drying this. Further, by applying pressure to the resultingnegative electrode, film thickness or a bulk density of the negativeelectrode active material layer may be adjusted.

A thickness of the negative electrode active material layer is at onesurface preferably equal to or more than 10 μm and equal to or less than70 μm, and more preferably equal to or more than 20 μm and equal to orless than 60 μm. When the thickness is equal to or more than 10 μm,desirable charging and discharging capacitances can be performed. On theother hand, when the thickness is equal to or less than 70 μm, the cellvolume can be decreased, thereby the energy density can be increased. Inthe case that pores exist in the power collector, the thickness of thenegative electrode active material layer at one surface of the layer isregarded as an average thickness of a portion of the power collector nothaving the pores.

<Separator>

The positive electrode precursor and the negative electrode arelaminated or rolled via the separator to form an electrode laminatedbody having the positive electrode precursor, the negative electrode andthe separator.

As the separator, there can be used a microporous film made ofpolyethylene, or a microporous film made of polypropylene which is usedin lithium ion secondary batteries, or nonwoven paper made of cellulosewhich is used in an electric double layer capacitor, or etc. A filmcomposed of organic or inorganic fine particles may be laminated on onesurface or both surfaces of these separators. Organic or inorganic fineparticles may be contained inside the separator.

A thickness of the separator is preferably equal to or more than 5 μmand equal to or less than 35 μm. When the thickness is equal to or morethan 5 μm, self-discharging by micro-short occurred inside tends todecrease. On the other hand, the thickness equal to or less than 35 μmis preferable, since output characteristics of the storage element tendsto be enhanced.

It is preferable that the film composed of organic or inorganic fineparticles is equal to or more than 1 μm and equal to or less than 10 μm.The thickness is preferably equal to or more than 1 μm, sinceself-discharging caused by micro-short occurred in an inside sectiontends to decrease. On the other hand, the thickness is preferably equalto or less than 10 μm, since output characteristics of the storageelement tend to be enhanced.

<Casing>

As the casing, a metal can, a laminated film, and etc. can be used.

The metal can made of aluminum is preferable.

A film laminated with a metal foil and a resin film are preferable, andthe one having a three-layer constitution composed of the outer layerresin film/the metal foil/the inner resin film is exemplified as anexample. The outer layer resin film is the one for preventing the metalfoil from receiving damage by contact, etc., and a resin such as nylon,polyester, or etc. is suitable for use. The metal foil is the one forpreventing permeation of moisture and gas, and a copper foil, aluminum,stainless steel, and etc. are suitable for use. The inner resin film isthe one for protecting the metal foil from an electrolytic solutionwhich is accommodated inside as well as for melt-sealing the casing, anda polyolefin, an acid-modified polyolefin, and etc. are suitable foruse.

[Electrolytic Solution]

The electrolytic solution in the present embodiment is a nonaqueouselectrolytic solution. Namely, this electrolytic solution contains anonaqueous solvent. The nonaqueous electrolytic solution contains equalto or more than 0.5 mol/L of an alkali metal salt, based on total amountof the nonaqueous electrolytic solution. Namely, the nonaqueouselectrolytic solution contains as an electrolyte the alkali metal salt.The nonaqueous solvent contained in the nonaqueous electrolytic solutionincludes, for example, a cyclic carbonate represented by ethylenecarbonate, propylene carbonate, and etc., and a linear carbonaterepresented by dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, and etc.

As the electrolyte salt containing the alkali metal ions which issoluble in the aforementioned nonaqueous solvent, for example, MFSI,MBF₄, MPF₆, and etc. can be used, where M is Li, Na, K, Rb, or Cs. Thenonaqueous electrolytic solution in the present embodiment can containat least one or more kinds of the alkali metal ions, and may alsocontain two or more kinds of the alkali metal salts or the alkali metalsalts as well as an alkaline earth metal salt selected from a berylliumsalt, a magnesium salt, a calcium salt, a strontium salt, and a bariumsalt. When two or more kinds of the alkali metal salts are contained inthe nonaqueous electrolytic solution, viscosity increase under lowtemperatures can be suppressed due to the presence of cations havingdifferent Stokes radii in the nonaqueous electrolytic solution, therebylow temperature characteristics of the nonaqueous hybrid capacitor areenhanced. When the alkaline earth metal ions other than the alkali metalions are contained in the nonaqueous electrolytic solution, acapacitance of the nonaqueous hybrid capacitor becomes larger, sinceberyllium ions, magnesium ions, calcium ions, strontium ions, and bariumions are divalent cations.

Although a method for containing the aforementioned two or more kinds ofthe alkali metal salts in the nonaqueous electrolytic solution or amethod for containing the alkali metal salt and the alkaline earth metalsalt in the nonaqueous electrolytic solution is not particularlyrestricted, the alkali metal salts composed of two or more kinds of thealkali metal ions may be dissolved, in advance in the nonaqueouselectrolytic solution or the alkali metal salt and the alkaline earthmetal salt may also be dissolved. In addition, the method in which thefollowing compounds are decomposed in the pre-doping step (to bedescribed later) is also included, i.e., a method for containing in thepositive electrode precursor a carbonate salt such as M₂CO₃, an oxidesuch as M₂O, an hydroxide such as MOH, a halide such as MF or MCI, and acarboxylate salt such as RCOOM (wherein R is H, an alkyl group, or anaryl group), where M in the above formula is denoted by one or morekinds selected from Na, K, Rb, and Cs, and/or the alkaline earth metalcarbonate salt selected from BeCO₃, MgCO₃, CaCO₃, SrCO₃, and BaCO₃, analkaline earth metal oxide, an alkaline earth metal hydroxide, analkaline earth metal halide, and an alkaline earth metal carboxylatesalt.

A concentration of the electrolyte salt in the electrolytic solution ispreferably in a range of 0.5 to 2.0 mol/L. When the concentration isequal to or higher than 0.5 mol/L, anions are present in a sufficientamount, and a capacitance of the nonaqueous hybrid capacitor holds. Onthe other hand, when the concentration is equal to or lower than 2.0mol/L, the salt is sufficiently dissolved in the electrolytic solution,and desirable viscosity and conductivity of the electrolytic solutiondesirably are held.

In the case where two or more kinds of the alkali metal salts arecontained or in the case where the alkali metal salt and the alkalineearth metal salt are contained in the nonaqueous electrolytic solution,the total concentration of these salts is preferably equal to or higherthan 0.5 mol/L, and more preferably in a range of 0.5 to 2.0 mol/L.

Lewis acid, Lewis base, or etc. is preferably added to the nonaqueouselectrolytic solution.

By adding Lewis acid, it becomes coordinated to an anion of the alkalimetal compound, thus an oxidation reaction can be promoted, since HOMO(Highest Occupied Molecular Orbital) of the anion is decreased. Lewisacid is not particularly restricted, as long as it is capable of forminga complex with the anion of the alkali metal compound. There can beused, for example, a phosphine complex such as a monophosphine metalcomplex having triphenylphosphine, etc. as a ligand and a diphosphinemetal complex having BINAP, etc. as the ligand; an amine complex such asan amine metal complex having trimethylamine, etc. as the ligand and adiamine metal complex having TMEDA (tetramethyl ethylenediamine), etc.as the ligand; an imine metal complex having pyridine or porphyrin asthe ligand; a metallocene complex having cyclopentadienyl group as theligand; an oxalato complex; a cyanato complex; a nitro complex; an acac(acetylacetone) complex; a carbonyl complex; an amino acid complex; analkenyl complex; an alkynyl complex, etc. Complexes containing one, twoor more kinds of these ligands may also be used, and in addition, theseligands may be modified by a functional group of a halogen atom such asfluorine and chlorine; an alkyl group such as methyl group; an arylgroup such as phenyl group; an alkoxy group such as methoxy group; asulfonyl group; amino group; a carboxyl group; a hydroxy group, etc.

As primary central metals of these Lewis acids, there can be used, forexample, boron, aluminum, scandium, titanium, vanadium, chromium,manganese, iron, cobalt, nickel, copper, zinc, zirconium, molybdenum,ruthenium, rhodium, palladium, silver, iridium, platinum, gold, and etc.

As Lewis acid, a metal oxide such as aluminum oxide, manganese oxide,magnesium oxide, zinc oxide, boron oxide, and etc. can also be used.

On the other hand, by addition of Lewis base to the nonaqueouselectrolytic solution, dissolution equilibrium of the alkali metalcompound is shifted, and dissolution of the alkali metal compound intothe electrolytic solution proceeds, therefore the oxidation reaction canbe accelerated. Lewis base is not particularly restricted as long as itis capable of forming a complex with the alkali metal ions. For example,an ether-type compound such as a crown ether, furan, and etc. issuitable for use. Among them, the crown ether is preferable. Inparticular, when lithium carbonate is used as the alkali metal compound,12-crown-4-ether is suitable for use, because it is capable of forming astable complex with lithium ions.

An amount of Lewis acid used is preferably 0.5% by weight to 5% byweight, and more preferably 1% by weight to 4% by weight based on atotal weight of the nonaqueous electrolytic solution. The acid ispreferably used within this range because pre-doping of the alkali metalions to the negative electrode can proceed under a milder conditionwithout impairing superior self-discharging characteristics of thenonaqueous hybrid capacitor.

An amount of Lewis base used is preferably 1.0% by weight to 10.0% byweight, and more preferably 2% by weight to 8% by weight based on atotal weight of the nonaqueous electrolytic solution. The base ispreferably used in this range, which enables to receive advantage ofpromoting pre-doping of the alkali metal ions to the negative electrodeor which proceeds under milder condition without impairingself-discharging characteristics of the nonaqueous hybrid capacitor.

<Production Method for Nonaqueous Hybrid Capacitor>

The nonaqueous hybrid capacitor in the third aspect of the presentinvention can be produced by the following steps using the positiveelectrode precursor and the negative electrode fabricated as above:

(1) a step of accommodating into the casing the laminated body composedof the positive electrode precursor comprising the positive electrodeactive material and the alkali metal compound, the negative electrode,and the separator (an assembling step),(2) a step of pouring the nonaqueous electrolytic solution inside thecasing (liquid pouring, impregnation, and encapsulation steps), and(3) a step of decomposing the alkali metal compound by applying avoltage between the positive electrode precursor and the negativeelectrode in this order as described above (pre-doping step),

wherein the ratio of the aforementioned A₁ (g/m²) to the aforementionedG₁ (Ah/m²), A₁/G, is equal to or larger than 1.0 (g/Ah) and equal to orsmaller than 2.0 (g/Ah), and the voltage applied in the pre-doping stepis equal to or higher than 4.2 V.

[Assembling Step]

An electrode laminated body obtained in the assembling step is a bodywhich is fabricated by laminating via the separator, the positiveelectrode precursor and the negative electrode, both of which are cut ina sheet fashion, and is connected with a positive electrode terminal anda negative electrode terminal. An electrode roll is a roll which isfabricated by winding up the positive electrode precursor and thenegative electrode via the separator, and is connected with the positiveelectrode terminal and the negative electrode terminal. The electroderoll may be fabricated in a cylinder or a flat fashion.

Although a connection method of the positive electrode terminal and thenegative electrode terminal is not particularly restricted, and a methodsuch as resistance welding or ultrasonic welding, and etc. can beadopted.

The electrode laminated body or the electrode roll which is connectedwith the terminals is preferably dried to remove a residual solvent. Adrying method is not particularly restricted, and drying is carried outby vacuum drying, etc. The residual solvent is preferably equal to orless than 1.5% with respect to a weight of the positive electrode activematerial layer or the negative electrode active material layer. Theresidual solvent more than 1.5% is not preferable because the solventremaining inside the body deteriorates self-discharging characteristics.

The dried electrode laminated body or the dried electrode roll which isaccommodated in the casing such as a metal can or a laminated film undera dry environment having a dew point of −40° C. or lower is preferablyencapsulated in a state of being open at one side of the body or roll. Atemperature higher than a dew point of −40° C. is not preferable becausemoisture adheres to the electrode laminated body or the electrode roll,and water remaining inside the body deteriorates self-dischargingcharacteristics. An encapsulation method of the casing is notparticularly restricted, and a method such as heat-seal or impulse seal,and etc. can be adopted.

[Liquid Pouring, Impregnation, and Encapsulation Steps]

After the assembling step, the nonaqueous electrolytic solution ispoured into the electrode laminated body accommodated in the casing.After the liquid pouring step, it is preferable to further impregnatethe body, followed by immersing sufficiently the positive electrode, thenegative electrode, and the separator with the nonaqueous electrolyticsolution. In a state that portions of the positive electrode, thenegative electrode, and the separator are not immersed with thenonaqueous electrolytic solution, doping proceeds irregularly in alithium doping step (to be described later), thereby resistance of theresulting nonaqueous hybrid capacitor may increase or durability thereofmay decrease. Although a method of the impregnation is not particularlyrestricted, for example, there can be used a method for installing thenonaqueous hybrid capacitor to a pressure reduction chamber after theliquid pouring in a state that the casing is opened, by setting thechamber to reduced atmosphere with a vacuum pump, and then returningagain to atmospheric pressure, etc. After completion of the impregnationstep, the nonaqueous hybrid capacitor, in a state that the casing isopened, is sealed by encapsulation under reduced pressure.

[Pre-Doping Step]

As a preferable step in the pre-doping, by decomposing the alkali metalcompound in the positive electrode precursor after applying a voltagebetween the positive electrode precursor and the negative electrode, thealkali metal ions are released by the decomposition of the alkali metalcompound in the positive electrode precursor, and the alkali metal ionsare reduced at the negative electrode, thereby the alkali metal ions arepre-doped to the negative electrode active material layer.

In the production method of the nonaqueous hybrid capacitor of thepresent invention, the voltage applied between the positive electrodeprecursor and the negative electrode in the pre-doping step ispreferably equal to or higher than 4.2 V. This voltage is preferably 4.2to 5.0 V, and more preferably 4.3 to 4.9 V.

A voltage applying method is not particularly restricted, and there canbe used a method of applying the constant voltage of equal to or higherthan 4.2 V using a charging and discharging apparatus, a power source,etc.; a method for superimposing a pulse voltage in applying theconstant voltage of equal to or higher than 4.2 V; a method for carryingout charging and discharging cycle in the voltage range including thevoltage of equal to or higher than 4.2 V using a charging anddischarging apparatus, etc.

In this pre-doping step, gas such as CO₂ is generated, which isaccompanied by oxidative decomposition of the alkali metal compound inthe positive electrode precursor. Thus, when applying a voltage, it ispreferable to take means for releasing the generated gas outside thecasing. There are included, for example,

a method for applying a voltage in a state that a part of the casing isopened;

a method for applying a voltage in a state that a suitable gas releasingmeans such as a gas venting valve, a gas permeation film, etc. areinstalled in advance to a part of the casing.

(Relation Between A₁ and G₁)

A₁ or G₁ is preferably adjusted so that A₁/G₁ is equal to or larger than1.0 (g/Ah) and equal to or smaller than 2.0 (g/Ah), where A₁ (g/m²) is aweight of the alkali metal compound per unit area in the aforementionedpositive electrode precursor, and G₁ (Ah/m²) is a capacitance per unitarea in the aforementioned negative electrode. When A₁/G₁ is equal to orlarger than 1.0 (g/Ah), an energy density of the nonaqueous hybridcapacitor can be enhanced, because a sufficient amount of the alkalimetal ions can be pre-doped to the negative electrode. When A₁/G₁ isequal to or smaller than 2.0 (g/Ah), pre-doping of an excessive amountof the alkali metal ions to the negative electrode can be suppressed,and precipitation of the alkali metal onto the electrode can also besuppressed.

The capacitance (G₁) per unit area in the negative electrode can bedetermined by the following method.

An electrochemical cell is prepared by cutting out the negativeelectrode prepared as above in a constant area (defining as P (cm²)) asan operation electrode, using metal lithium as each of a counterelectrode and a reference electrode, and also using a nonaqueous solventcontaining a lithium salt as the electrolytic solution. By using acharging and discharging apparatus, after the constant current chargingfor the electrochemical cell is carried out up to the voltage of 0.01 Vunder the current of 0.5 mA/cm² at 25° C., the constant voltage chargingis carried out down to the current value of 0.01 mA/cm². The sum ofcharging capacitances in these constant current charging and constantvoltage charging is obtained, and evaluated as a capacitance, Q (Ah) ofthe negative electrode. The capacitance (G₁) obtained per unit area ofthe negative electrode can be calculated by Q/P using the resulting Pand Q.

The amount (A₁) of the lithium compound per unit area in the positiveelectrode precursor can be adjusted in preparation of the aforementionedslurry for fabricating the positive electrode precursor by taking anamount of the lithium compound as well as an amount of the slurry whichis coated onto the positive electrode power collector. The capacitanceG₁ per unit area of the negative electrode can be adjusted by selectinga kind and an amount of the negative electrode active material which isused in preparation for the negative electrode as well as an amount ofthe slurry which is coated on to the negative electrode power collector.

[Aging Step]

Aging is preferably carried out for the nonaqueous hybrid capacitorafter the pre-doping step. In the aging step, a solvent in theelectrolytic solution is decomposed at the negative electrode, and asolid polymer coating film having permeability for alkali metal ions isformed at a surface of the negative electrode.

A method of the aforementioned aging is not particularly restricted, andfor example, a method of reacting a solvent in the electrolytic solutionunder a high temperature environment, etc. can be used.

[Gas Venting Step]

It is preferable to completely remove remaining gas in the electrolyticsolution, the positive electrode, and the negative electrode by furthercarrying out gas venting after completion of the aging step. In a statethat the gas remains at least in a part of the electrolytic solution,the positive electrode, and the negative electrode, ion conductivity isprevented, thereby resistance of the resulting nonaqueous hybridcapacitor is increased.

A method of the gas venting is not particularly restricted, and therecan be used, for example, a method of installing the nonaqueous hybridcapacitor in a pressure reduction chamber in a state that the casing isopened, and setting the chamber to a reduced pressure atmosphere byusing a vacuum pump, etc.

[Nonaqueous Hybrid Capacitor]

From all those methods described above, the nonaqueous hybrid capacitorcan be produced.

This storage element is provided with the positive electrode having theporous positive electrode active material layer with voids which werepreviously filled with the alkali metal compound in the positiveelectrode precursor, and as a consequence removed by decomposition ofthe compound, and also the negative electrode having the negativeelectrode active material layer doped with the alkali metal compound asa dopant source.

[Positive Electrode]

An average pore diameter of the voids in the positive electrode activematerial layer of the positive electrode is preferably 0.1 to 10 μm, andmore preferably 0.3 to 5 μm. A void ratio of the positive electrodeactive material layer is preferably 10 to 60%, and more preferably 15 to50%.

A bulk density of the positive electrode active material layer ispreferably equal to or higher than 0.30 g/cm³, and more preferably in arange of equal to or higher than 0.40 g/cm³ to equal to or lower than1.3 g/cm³. When the bulk density of the positive electrode activematerial layer is equal to or higher than 0.30 g/cm³, a high energydensity can be obtained, and the storage element can be madesmall-sized. When this bulk density is equal to or lower than 1.3 g/cm³,the electrolytic solution diffuses sufficiently inside the voids in thepositive electrode active material layer, thereby high outputcharacteristic is exhibited.

[Negative Electrode]

An amount of pre-doping of the alkali metal ions to the negativeelectrode active material in the negative electrode is preferably 50 to100%, and more preferably 60 to 98% with respect to the capacitance, Qof the negative electrode.

A bulk density of the negative electrode active material layer ispreferably equal to or higher than 0.50 g/cm³ and equal to or lower than1.8 g/cm³, and further preferably equal to or higher than 0.60 g/cm³ andequal to or lower than 1.5 g/cm³. When the bulk density is equal to orhigher than 0.50 g/cm³, sufficient strength is held as well assufficient conductivity between active materials can be exhibited. Whenit is equal to or lower than 1.8 g/cm³, the sufficient volume of voidsin which ions are capable of diffusing well inside the active materiallayer is ensured.

[Characteristics Evaluation of Storage Element] (Static Capacitance)

In the present specification, a static capacitance, Fa (F) is a valueobtained by the following method:

First, charging under a constant current is carried out in a thermostatchamber set at 25° C. for a cell corresponding to the nonaqueous hybridcapacitor up to 3.8 V under the current value of 2C, followed bycharging under the constant voltage of 3.8 V for 30 minutes in total.After that, discharging down to 2.2 V under the constant current of 2Cis carried out, and the capacitance obtained here is defined as Q(C).The static capacitance Fa is a value calculated by Fa=Q/ΔVx=Q/(3.8−2.2)using Q obtained here as well as the voltage change, ΔVx (V).

In the present specification, 1C is defined as the current value whendischarging is completed within 1 hour in carrying out discharging underthe constant current from the upper limit voltage of 3.8 V to the lowerlimit voltage of 2.2 V.

<Identification Method for Alkali Metal Compound in Electrode>

An identification method of the alkali metal compound contained in thepositive electrode is not particularly restricted, and it can beidentified, for example by the following method. The alkali metalcompound is preferably identified by a combination of a plural ofanalysis means described below.

In the ion chromatography to be described later, anions can beidentified by analysis of the water obtained after washing the positiveelectrode with distilled water.

When the alkali metal compound cannot be identified by theaforementioned analysis means, it can also be identified by using7Li-solid state NMR, XRD (X-ray diffraction), TOF-SIMS (Time ofFlight-Secondary Ion Mass Spectrometry), AES (Auger ElectronSpectroscopy), TPD/MS (Thermally Programmed Desorption/MassSpectrometry), DSC (Differential Scanning Calorimetry), and etc. asother analysis means.

[Scanning Electron Microscope-Energy-Dispersive X-Ray Spectroscopy(SEM-EDX)]

The alkali metal compound and the positive electrode active material canbe discriminated in oxygen mapping using the SEM-EDX image of thesurface of the positive electrode, measured by setting the observationmagnification to 1000 times to 4000 times. As a measurement example ofthe SEM-EDX image, it can be measured under the conditions of anacceleration voltage of 10 kV, an emission current of 10 μA, ameasurement pixel number of 256×256 pixels, and an integration number of50 times. In order to prevent electrification of the sample it may besubjected to surface treatment by vacuum deposition or sputtering, etc.of gold, platinum, osmium, and etc. For a measurement method of theSEM-EDX image, brightness as well as contrast is preferably adjusted sothat there are no pixels showing the maximum brightness value in themapping image, and the average value of brightness values falls within arange of 40% to 60% for the maximum brightness value. Such a particlehaving an area of oxygen equal to or more than 50% of a bright partwhere the luminance values of oxygen are binarized based on the averageluminance value of oxygen in the resulting oxygen mapping, can bediscriminated as the alkali metal compound.

[Microscopic Raman Spectrometry]

The alkali metal compound and the positive electrode active material canbe discriminated by Raman imaging of carbonate ions at the surface ofthe positive electrode, measured by setting the observationmagnification to 1000 times to 4000 times. As examples of measurementconditions, they can be measured under the conditions as 532 nmexcitation light, excitation light intensity of 1%, a long operation ofan objective lens by 50 times, a diffraction lattice of 1800 gr/mm, amapping system of point scanning (a slit with 65 mm, a binning with 5pix), a 1 mm step, 3 second exposure time per one point, one time of anintegration number, and a noise filter present. In the Raman spectrummeasured by setting a straight base line in a range of 1071 to 1104cm⁻¹, the area of carbonate ion peaks having positive values for thebaseline is approximated to an integrated frequency distribution byassuming the peak shape of the area as a Gaussian type peak, and thefrequencies attributable to the noises in the frequency distribution aresubtracted from the distribution.

[X-Ray Photoelectron Spectroscopy (XPS)]

The bonding state of compounds contained in the positive electrodeprecursor can be discriminated by analysis of an electron state of thecompounds in the positive electrode precursor using XPS. As an exampleof measurement conditions, it can be measured under the conditions of anX-ray source of monochromatic AIKα, an X-ray beam diameter of 100 μmϕ(25 W, 15 kV), a path energy of narrow scan: 58.70 eV, theelectrification neutralization presents, sweep number of narrow scan: 10times (carbon, oxygen), 20 times (fluorine), 30 times (phosphorous), 40times (alkali metal), 50 times (silicon), an energy step of narrow scan:0.25 eV. The positive electrode surface is preferably cleaned bysputtering before XPS measurement. As an example, the positive electrodesurface in a range of 2 mm×2 mm can be cleaned under the sputteringconditions of an acceleration voltage of 1.0 kV for 1 minute (1.25nm/min as converted to that for SiO₂). In the resulting XPS spectrum,each peak is assigned as follows: a peak having the bonding energy ofLi1s of 50 to 54 eV as LiO₂ or Li—C bonding, a peak of 55 to 60 eV asLiF, Li₂CO₃, and Li_(x)PO_(y)F_(z) (x, y, z are integers from 1 to 6), apeak having the bonding energy of C1s of 285 eV as C—C bonding, a peakof 286 eV as C—O bonding, a peak of 288 eV as COO, a peak of 290 to 292eV as CO₃ ²⁻ and C—F bonding, a peak having the bonding energy of O1s of527 to 530 eV as O²⁻ (Li₂O), a peak of 531 to 532 eV as CO, CO₃, OH,PO_(x) (x is an integer from 1 to 4), and SiO_(x) (x is an integer from1 to 4), a peak of 533 eV as C—O and SiO_(x) (x is an integer from 1 to4), a peak having the bonding energy of F1s of 685 eV as LiF, a peak of687 eV as C—F boning, for the bonding energies of Li_(x)PO_(y)F_(z) (x,y, z are integers from 1 to 6), PF₆ ⁻, and P2p, a peak of 133 eV asPO_(x) (x is an integer from 1 to 4), a peak of 134 to 136 eV as PF_(x)(x is an integer from 1 to 6), a peak having the bonding energy Si2p of99 eV as Si, silicide, a peak of 101 to 107 eV as Si_(x)O_(y) (x, y arearbitrary integers). When the peaks overlap with each other in thespectrum, it is preferable to assign the spectrum by separating thepeaks assuming a Gaussian function type peak or a Lorentz function typepeak. The alkali metal compound present can be identified from themeasurement result of the electron state obtained above and the ratio ofthe elements present.

[Ion Chromatography]

By analyzing ion-chromatographically the washing solution obtained bywashing the positive electrode by distilled water, anion species elutedin the water can be identified. A column such as an ion exchange-type,an ion exclusion-type, or a reversed phase ion pair-type can be used. Anelectric conductivity detector, a UV/visible ray absorbance detector, anelectrochemical detector, and etc. can be used as a detector, and asuppressor apparatus installed with a suppressor in front of thedetector, or a non-suppressor apparatus in which a solution having lowelectric conductivity is used as eluent without the suppressor can beused. Measurement using the detector can also be carried out bycombination of a mass spectrometer and a detector of charged particles.

Holding time of the sample is constant for each of the ion species, whenconditions of the column, the eluent, and etc. are once fixed, and peakresponses differ for each of the ion species, however are proportionalto the concentration. Qualitative and quantitative analyses ofcomponents of the ion species are possible by measuring, in advance, astandard solution having a known concentration where traceability isensured.

<Quantitative Method for Alkali Metal Compound: Calculation of a, B, A₁,B₁, and X>

Described below is a quantitative method of the alkali metal compoundcontained in the positive electrode precursor. The alkali metal compoundcan be quantitatively determined by washing the positive electrodeprecursor with distilled water, and measuring a weight change of thepositive electrode before and after washed by the distilled water. AreaY (cm²) of the positive electrode precursor to be measured is notparticularly restricted, however, from the view point of reducingmeasurement variation, it is preferable to be equal to or larger than 5cm² and equal to or smaller than 200 cm², and further preferable to beequal to or larger than 25 cm² and equal to or smaller than 150 cm².When the area is equal to or larger than 5 cm², the measurement valuesare reproducible. When the area is equal to or smaller than 200 cm², thesample is superior in handling for the measurement.

Described below is calculation methods for A (g/m²), a weight of thealkali metal compound in the positive electrode active material layer atone surface of the positive electrode precursor, and B (g/m²), a weightof the positive electrode active material in the positive electrodeactive material layer of the positive electrode precursor.

In the case of the positive electrode precursor with the electrode inwhich the positive electrode active material layer is coated on bothsurfaces of the positive electrode power collector, the weight of thematerial layer which is removed from on either one of the surfaces ofthe precursor by using a spatula, a brush, and etc., is identified asthe weight (M₀ (g)) of the positive electrode precursor which was cut ina size of an area Y. In the case of the electrode in which the positiveelectrode active material layer is coated only on one surface of thepositive electrode power collector is defined as M₀ (g) of the weight ofthe sample cut in the size of area Y. Subsequently, the positiveelectrode precursor is fully immersed in distilled water whose amount is100 times of that of the positive electrode precursor (100 M₀ (g)) forequal to or longer than 3 days under an environment of 25° C., and thenthe alkali metal compound is eluted into the water. It is preferable inthis case to take measures for putting a lid on the container so thatthe distilled water does not volatilize. After immersing it for equal toor longer than 3 days, the positive electrode precursor is taken outfrom the distilled water (when the aforementioned ion chromatographymeasurement is carried out, the solution amount is adjusted so that theamount of distilled water is 100 M₀ (g)), followed by vacuum drying. Theconditions of the vacuum drying are preferable as follows: temperaturerange from 100 to 200° C., a pressure from 0 to 10 kPa, drying time from5 to 20 hours when the amount of residual moisture in the positiveelectrode precursor becomes equal to or lower than 1% by weight. Aresidual amount of moisture can be quantitatively determined by the KARLFISCHER method. A weight of the positive electrode precursor after thevacuum drying is defined as M₁ (g), and subsequently, for the purpose ofmeasuring the weight of the positive electrode power collector in theprecursor, the remaining positive electrode active material layer on thepositive electrode power collector is removed using a spatula, a brush,and etc. When the weight of the resulting positive electrode powercollector is defined as M₂ (g), A (g/m²), i.e., the weight of the alkalimetal compound in the active material layer at one surface of thepositive electrode precursor, B (g/m²), the weight of the activematerial contained in the active material layer at one surface of thepositive electrode, and the weight ratio X (% by weight) of the alkalimetal compound contained in the active material layer of the positiveelectrode precursor can be calculated by the equations (3), (4), and(5), respectively.

[Equation 3]

A=10000×(M ₀ −M ₁)/Y  (3)

[Equation 4]

B=10000×(M ₁ −M ₂)/Y  (4)

[Equation 5]

X=100×(M ₀ −M ₁)/(M ₀ −M ₂)  (5)

It should be noted that A₁ which is a weight of the alkali metalcompound per unit volume of the positive electrode precursor correspondsto the aforementioned A, and B₁ which is a weight of the positiveelectrode active material per unit area corresponds to theaforementioned B.

<Quantitative Method of Alkali Metal Element: ICP-MS>

The positive electrode precursor is oxidatively decomposed using astrong acid such as concentrated nitric acid, concentrated hydrochloricacid, nitrohydrochloric acid, and etc., and the resulting solution isdiluted with pure water so as to obtain an acid concentration of 2% to3%. In the oxidative decomposition, heat and pressure can also beapplied as appropriate. The resulting diluted solution is analyzed usingICP-MS, in which a known amount of an element is preferably added as aninternal standard. When the alkali metal elements as measurement objectsare present in concentration of equal to or higher than the measurementupper limit, it is preferable to further dilute the solution, whilekeeping the acid concentration. Each element can be quantitativelydetermined based on a calibration curve which is prepared in advance byusing a standard solution for chemical analysis.

EXAMPLES

Features of the present invention will be clarified further below withreference to Examples and Comparative Examples. The present invention,however, should not be limited to the following Examples.

The following provides a detailed explanation of the embodiment in thefirst aspect of the present invention.

Example 1 Preparation of Positive Electrode Active Material PreparationExample 1a

A carbide was obtained by carbonization treatment of a crushed coconutshell carbide in a compact-type carbonization furnace at 500° C. for 3hours under a nitrogen atmosphere. The resulting carbide was put insidean activation furnace where steam which was heated in a preheatingfurnace was introduced to the activation furnace in a warm state at arate of 1 kg/h, and activated by increasing a temperature up to 900° C.over a period of 8 hours. The carbide after activation was taken out,and cooled it down under a nitrogen atmosphere, from which an activatedcarbon was obtained. The resulting activated carbon was washed in apassing water bath for 10 hours. After the activated carbon was driedfor 10 hours in an electric drying machine at 115° C., it was crushedfor 1 hour using a ball mill, and then activated carbon 1 was obtained.

The average particle diameter of this activated carbon 1 was 4.2 μmmeasured by using a laser diffraction-type particle size distributionmeasurement apparatus (SALD-2000), manufactured by Shimadzu Corp. Thefine pore distribution thereof was measured using a fine poredistribution measurement apparatus (AUTOSORB-1, AS-1-MP, manufactured byYuasa Ionics Co., Ltd.), and the BET specific area was found to be 2360m²/g, the mesopore volume (V₁) 0.52 cc/g, the micropore volume (V₂) 0.88cc/g, and V₁/V₂=0.59.

Preparation Example 2a

A carbide having an average particle diameter of 7 μm was obtained bycarrying out carbonization of a phenol resin in a furnace at 600° C. for2 hours under a nitrogen atmosphere, crushing it using a ball mill,followed by classification of the carbide. Activation was carried out bymixing the carbide and KOH in the weight ratio of 1:5, and heating themixture at 800° C. for 1 hour in the furnace under a nitrogenatmosphere. Then, activated carbon 2 was obtained by washing it understirring for 1 hour in diluted hydrochloric acid whose concentration wasadjusted to that of 2 mol/L, washing with distilled water under boilingin which pH is held in a range of pH 5 to 6, and then carrying outdrying.

The average particle diameter of activated carbon 2 was 7.0 μm measuredby using a laser diffraction-type particle size distribution measurementapparatus (SALD-2000), manufactured by Shimadzu Corp. The fine poredistribution thereof was measured using a fine pore distributionmeasurement apparatus (AUTOSORB-1, AS-1-MP, manufactured by Yuasa IonicsCo., Ltd). The BET specific area was 3627 m²/g, the mesopore volume (V₁)1.50 cc/g, the micropore volume (V₂) 2.28 cc/g, and V₁/V₂=0.66.

[Crushing of Lithium Carbonate]

After cooling 20 g of lithium carbonate having an average particlediameter of 53 μm from 25° C. down to −196° C. by liquid nitrogen in acrushing machine, manufactured by IMEX Co., Ltd., lithium carbonate 1having an average particle diameter of 2.5 μm was obtained by crushingit with zirconia beads having a diameter of 1.0 mm at a peripheral speedof 10.0 m/s for 30 minutes.

[Production of Positive Electrode Precursor]

A positive electrode precursor was produced using activated carbon 1 asthe positive electrode active material and the lithium carbonate 1 asthe alkali metal compound.

A coating solution was obtained by mixing 55.5 parts by weight ofactivated carbon 1, 32.0 parts by weight of lithium carbonate 1, 3.0parts by weight of Ketjen black, 1.5 parts by weight of PVP (polyvinylpyrrolidone), and 8.0 parts by weight of PVDF (polyvinylidene fluoride)as well as a mixed solvent of NMP (N-methylpyrrolidone) and pure waterin a weight ratio of 99:1, and dispersing them using a thin-filmspin-type high speed mixer, Filmix, manufactured by PRIMIX Co., Ltd.under the condition of a peripheral speed of 17 m/s. The viscosity (ηb)and the value (TI) of the resulting coating solution were measured usingan E-type viscometer, TVE-35H, manufactured by Touki Sangyo Co., Ltd.The viscosity (ηb) was 2,850 mPa·s, and the value (TI) 4.4. Dispersityof the resulting coating solution was measured using a particle gauge,manufactured by YOSHIMITSU SEIKI Co., Ltd. The particle size was 31 μm.Positive electrode precursor 1 was obtained by setting a clearance of anapplicator in the following coating apparatus to 150 μm, coating thecoating solution on one surface of an aluminum foil having a thicknessof 15 μm under the condition of a coating speed of 1 m/min. by using anautomatic coating apparatus (PI-1210), manufactured by TESTER SANGYOCo., Ltd., and dying it at a drying temperature of 120° C. Positiveelectrode precursor 1 was subjected to roll-pressing under the conditionof a pressure of 6 kN/cm and a surface temperature of the pressing partas 25° C. A film thickness of the positive electrode active materiallayer in positive electrode precursor 1 was determined by subtractingthe thickness of the aluminum foil from the average value of thicknessesof positive electrode precursor 1 measured at arbitrary 10 points of theprecursor by using a film thickness meter, Linear Gauge Sensor, GS-551,manufactured by ONO SOKKI Co., Ltd. Then the film thickness of thepositive electrode active material layer was found to be 52 μm.

<Calculation of A, B>

Sample 1 was prepared by cutting positive electrode precursor 1 in asize of 10 cm×5 cm, and the weight M₀ thereof was measured to be 0.3104g. By immersing sample 1 in 31.0 g of distilled water under anenvironment of 25° C. for 3 days, lithium carbonate in sample 1 waseluted in the distilled water. Then sample 1 was taken out, and vacuumdried for 12 hours under conditions of 150° C. and 3 kPa. The weight, M₁at this time was 0.2424 g. After this, the active material layer on apositive electrode power collector was removed using a spatula or abrush, and the weight, M₂ of the positive electrode power collector inthis time measured was found to be 0.099 g. According to equations (3)and (4), the following calculation results were obtained: A=13.60 g/m²,B=28.68 g/m², and A/B=0.474.

<Calculation of C, D, and E>

Sample 2 was prepared by cutting positive electrode precursor 1 in asize of 4.0 cm×1.0 cm, and vacuum drying for 12 hours under conditionsof 150° C. and 3 kPa. The fine pore distribution was measured by a finepore distribution measurement apparatus (AUTOSORB-1, AS-1-MP,manufactured by Yuasa Ionics Co., Ltd.) by using sample 2 after thevacuum drying which was cut into eight equivalent parts with a size of0.5 cm×0.5 cm. The following calculation values were obtained: the BETspecific area was 13.84 m²/g, the mesopore volume 3.28 μL, the microporevolume 5.60 μL, C=3.46 m²/cm², D=0.82 μL/cm², and E=1.40 μL/cm².

<Calculation of Average Particle Diameter of Alkali Metal Compound>

A cross section perpendicular to the surface direction of the positiveelectrode, sample 1 was prepared by cutting the positive electrodeprecursor in a size of 0.5 cm×0.5 cm, and using SM-09020CP, manufacturedby JEOL under conditions of an acceleration voltage of 4 kV, a beamdiameter of 500 μm, and argon gas atmosphere. After this, SEM and EDX ofthe cross section of the positive electrode were measured by a methodshown below.

(SEM-EDX Measurement Condition)

Measurement apparatus: Field emission-type SEM, FE-SEM, S-4700,manufactured by Hitachi High-Technologies Corp. and energydispersion-type X-ray analysis apparatus, E MAX, manufactured by Horiba,Co., Ltd.

Acceleration voltage: 10 kV

Emission current: 10 μA

Measurement magnification: 2000 times

Electron beam incident angle: 90°

X-ray take out angle: 30°

Dead time: 15%

Mapping elements: C, O, F

Measurement pixel number: 256×256 pixels

Measurement time: 60 sec.

Integration number: 50 times

In the mapping image, brightness and contrast obtained were adjusted sothat there observed no pixels in the image showing the maximumbrightness value, and the average value of brightness values fell withina range of 40% to 60% of the maximum brightness value.

Image analysis for the resulting image of the cross section of thepositive electrode so measured by SEM and EDX was carried out usingimage analysis software (ImageJ). In the resulting oxygen mapping, theparticle containing an area of oxygen equal to or more than 50% of thebright part where luminance values of oxygen are binarized based on theaverage luminance value of oxygen, was defined as particle Z of lithiumcarbonate, the cross-sectional area T was determined for all of the Zparticles observed in the cross-sectional SEM image, and then theaverage particle diameter by equations (1) and (2) was found to be 2.3μm.

[Production of Negative Electrode]

A coating solution was obtained by mixing 84 parts by weight ofcommercial hard carbon (Carbotron, produced by Kureha Corp.), 10 partsby weight of acetylene black, 6 parts by weight of PVdF (polyvinylidenefluoride) as well as NMP (N-methylpyrrolidone), and dispersing themusing a thin film spin-type high speed mixer, Filmix, manufactured byPRIMIX Co., Ltd. under the condition of a peripheral speed of 17 m/s.Negative electrode 1 was obtained by setting a clearance of theapplicator in the following apparatus to 300 μm, coating the coatingsolution on one surface of an electrolytic copper foil having athickness of 10 μm under the condition of a coating speed of 1 m/min.using an automatic coating apparatus (PI-1210), manufactured by TESTERSANGYO Co., Ltd., and drying it at a drying temperature of 120° C.Resulting negative electrode 1 was subjected to roll-pressing under theconditions of a pressure of 5 kN/cm and a surface temperature of thepressing part as 25° C. The film thickness of the positive electrodeactive material layer in resulting negative electrode 1 was 30 μm.

[Preparation of Nonaqueous Hybrid Capacitor]

One sheet of positive electrode precursor 1 in which the positiveelectrode active material layer has a size of 10.0 cm×5.0 cm, one sheetof negative electrode 1 in which the negative electrode active materiallayer has a size of 10.1 cm×5.1 cm, and one sheet of the separator madeof polyethylene and having a size of 10.3 cm×5.3 cm (manufactured byAsahi Kasei, Corp., thickness 15 μm) were respectively prepared. Anelectrode laminated body was obtained by laminating them in the order ofpositive electrode precursor 1, the separator, and negative electrode 1.After the resulting electrode laminated body was connected with apositive electrode terminal and a negative electrode terminal byultrasonic welding, the body was put into a container made of analuminum laminate packaging material, and was heat-sealed for the threesides including the side with terminals. The nonaqueous hybrid capacitorwas prepared by pouring 3.5 g of a PC solution of LiPF₆ having anelectrolyte concentration of 1.2 M as a nonaqueous electrolytic solutionunder an atmospheric pressure at 25° C. into the electrode laminatedbody accommodated in the aluminum laminate packaging material under adry air environment having a dew point of −40° C. or lower.Subsequently, the nonaqueous hybrid capacitor was introduced to apressure reduction chamber, and a pressure was reduced from anatmospheric pressure to −87 kPa, and returned to an atmosphericpressure. After this, the capacitor was allowed to stand for 5 minutes.Then, a step of returning to an atmospheric pressure after reducing thepressure from an atmospheric pressure to −87 kPa was repeated fourtimes, followed by allowing the capacitor to stand for 15 minutes.Furthermore, after the pressure was reduced from an atmospheric pressureto −91 kPa, it was returned to an atmospheric pressure. Similarly, thestep of reducing the pressure and returning to an atmospheric pressurewas repeated seven times in total (each pressure was reduced to −95,−96, −97, −81, −97, −97, and −97 kPa, respectively). The nonaqueouselectrolytic solution was impregnated to the electrode laminated body bythe above steps.

After this, the nonaqueous hybrid capacitor was put in areduced-pressure sealing machine in which the pressure is in a state of−95 kPa, the aluminum laminate packaging material was encapsulated byapplying pressure of 0.1 MPa at 180° C. for 10 seconds.

[Pre-Doping Step]

The resulting nonaqueous hybrid capacitor was put into an argon boxhaving a temperature of 25° C., dew point −60° C., and an oxygenconcentration of 1 ppm. Doping of lithium to the negative electrode wascarried out by unsealing the aluminum laminate packaging materialaccommodating the nonaqueous hybrid capacitor, followed by cutting asurplus portion of the packaging material, carrying out initial chargingby a method of charging under the constant current of 50 mA up to 4.5 V,and subsequently charging under the constant voltage at 4.5 V for 2hours using a power source (P4LT18-0.2), manufactured by MatsusadaPrecision Inc. After completion of the lithium doping, the aluminumlaminate was encapsulated using a heat seal machine (FA-300),manufactured by FUJIIMPULSE Co., Ltd.

[Aging Step]

The nonaqueous hybrid capacitor after the lithium doping was taken outfrom the argon box, and then, by carrying out discharging under theconstant current of 50 mA down to 3.8 V under an environment of 25° C.,followed by carrying out discharging under the constant current down to3.8 V for 1 hour, the voltage was adjusted to 3.8 V. Subsequently, thenonaqueous hybrid capacitor was stored in a thermostat chamber set at60° C. for 8 hours.

[Gas Venting Step]

After the aging, a part of the aluminum laminate packaging materialaccommodating the nonaqueous hybrid capacitor was unsealed at atemperature of 25° C. under a dry air environment having a dew point of−40° C. or lower. Subsequently, the nonaqueous hybrid capacitor was putin a pressure reduction chamber, and the step was repeated in totalthree times, in which the pressure was reduced from an atmosphericpressure to −80 kPa for 3 minutes, and returned to an atmosphericpressure over a period of 3 minutes by using a diaphragm pump(manufactured by KNF Co., Ltd., N816. 3KT. 45. 18). Then, after puttingthe nonaqueous hybrid capacitor in a reduced-pressure sealing machine toreduce the pressure to −90 kPa, the aluminum laminate packaging materialwas encapsulated by sealing under a pressure of 0.1 MPa at 200° C. for10 seconds.

[Evaluation of nonaqueous hybrid capacitor][Measurement of static capacitance Fa]

The nonaqueous hybrid capacitor obtained in the previous step wassubjected to charging under the constant current of 2C (10 mA) up to 3.8V, and subsequently charging under the constant voltage by applying theconstant voltage of 3.8 V for 30 minutes in total using a charging anddischarging apparatus (ACD-01), manufactured by Aska Electronics Co.,Ltd. in a thermostat chamber set at 25° C. After this, discharging underthe constant current of 2C (10 mA) down to 2.2 V was carried out toobtain the capacitance, Q(C), and the static capacitance, Fa calculatedby F=Q/(3.8−2.2) was found to be 11.86 F.

Example 2

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 63.4 parts by weight of activated carbon 1,22.3 parts by weight of lithium carbonate 1, 3.4 parts by weight ofKetjen black, 1.7 parts by weight of PVP (polyvinyl pyrrolidone), and9.1 parts by weight of PVDF (polyvinylidene fluoride).

Example 3

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 67.3 parts by weight of activated carbon 1,17.5 parts by weight of lithium carbonate 1, 3.6 parts by weight ofKetjen black, 1.8 parts by weight of PVP (polyvinyl pyrrolidone), and9.7 parts by weight of PVDF (polyvinylidene fluoride).

Example 4

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 48.0 parts by weight of activated carbon 1,41.2 parts by weight of lithium carbonate 1, 2.6 parts by weight ofKetjen black, 1.3 parts by weight of PVP (polyvinyl pyrrolidone), and6.9 parts by weight of PVDF (polyvinylidene fluoride).

Example 5

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 41.3 parts by weight of activated carbon 1,49.4 parts by weight of lithium carbonate 1, 2.2 parts by weight ofKetjen black, 1.1 parts by weight of PVP (polyvinyl pyrrolidone), and6.0 parts by weight of PVDF (polyvinylidene fluoride).

Comparative Example 1

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 68.7 parts by weight of activated carbon 1,15.8 parts by weight of lithium carbonate 1, 3.7 parts by weight ofKetjen black, 1.9 parts by weight of PVP (polyvinyl pyrrolidone), and9.9 parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 2

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 69.9 parts by weight of activated carbon 1,14.3 parts by weight of lithium carbonate 1, 3.8 parts by weight ofKetjen black, 1.9 parts by weight of PVP (polyvinyl pyrrolidone), and10.1 parts by weight of PVDF (polyvinylidene fluoride) as well as amixed solvent of NMP (N-methylpyrrolidone) and pure water in a weightratio of 90:10, followed by dispersing the constituting substances toprepare the coating solution.

Comparative Example 3

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 72.7 parts by weight of activated carbon 1,11.0 parts by weight of lithium carbonate 1, 3.9 parts by weight ofKetjen black, 2.0 parts by weight of PVP (polyvinyl pyrrolidone), and10.5 parts by weight of PVDF (polyvinylidene fluoride) as well as amixed solvent of NMP (N-methylpyrrolidone) and pure water in a weightratio of 90:10, followed by dispersing the constituting substances toprepare the coating solution.

Example 6

A positive electrode precursor was prepared by using with respect to thecomposition of a coating solution of a positive electrode, 52.9 parts byweight of activated carbon 1, 35.2 parts by weight of lithium carbonate1, 2.9 parts by weight of Ketjen black, 1.4 parts by weight of PVP(polyvinyl pyrrolidone), and 7.6 parts by weight of PVDF (polyvinylidenefluoride). At this time, the positive electrode precursor having a filmthickness of the positive electrode active material layer of 101 μm wasprepared by setting a clearance of the applicator to 300 μm. Thereafter,a nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1.

Example 7

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 50.8 parts by weight of activated carbon 1,37.8 parts by weight of lithium carbonate 1, 2.7 parts by weight ofKetjen black, 1.4 parts by weight of PVP (polyvinyl pyrrolidone), and7.3 parts by weight of PVDF (polyvinylidene fluoride).

Example 8

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 67.6 parts by weight of activated carbon 1,17.2 parts by weight of lithium carbonate 1, 3.7 parts by weight ofKetjen black, 1.8 parts by weight of PVP (polyvinyl pyrrolidone), and9.7 parts by weight of PVDF (polyvinylidene fluoride).

Example 9

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 66.0 parts by weight of activated carbon 1,19.2 parts by weight of lithium carbonate 1, 3.6 parts by weight ofKetjen black, 1.8 parts by weight of PVP (polyvinyl pyrrolidone), and9.5 parts by weight of PVDF (polyvinylidene fluoride).

Comparative Example 4

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 66.0 parts by weight of activated carbon 1,19.2 parts by weight of lithium carbonate 1, 3.6 parts by weight ofKetjen black, 1.8 parts by weight of PVP (polyvinyl pyrrolidone), and9.5 parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 5

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 75.1 parts by weight of activated carbon 1, 8.0parts by weight of lithium carbonate 1, 4.1 parts by weight of Ketjenblack, 2.0 parts by weight of PVP (polyvinyl pyrrolidone), and 10.8parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 6

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 77.2 parts by weight of activated carbon 1, 5.5parts by weight of lithium carbonate 1, 4.2 parts by weight of Ketjenblack, 2.1 parts by weight of PVP (polyvinyl pyrrolidone), and 11.1parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Example 10

A positive electrode precursor was prepared by using with respect to thecomposition of a coating solution of a positive electrode, 54.2 parts byweight of activated carbon 1, 33.6 parts by weight of lithium carbonate1, 2.9 parts by weight of Ketjen black, 1.5 parts by weight of PVP(polyvinyl pyrrolidone), and 7.8 parts by weight of PVDF (polyvinylidenefluoride). At this time, the positive electrode precursor having a filmthickness of the positive electrode active material layer of 19 μm wasprepared by setting a clearance of the applicator to 60 μm. Thereafter,a nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1.

Example 11

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 46.3 parts by weight of activated carbon 1,43.2 parts by weight of lithium carbonate 1, 2.5 parts by weight ofKetjen black, 1.3 parts by weight of PVP (polyvinyl pyrrolidone), and6.7 parts by weight of PVDF (polyvinylidene fluoride).

Example 12

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 41.2 parts by weight of activated carbon 1,49.5 parts by weight of lithium carbonate 1, 2.2 parts by weight ofKetjen black, 1.1 parts by weight of PVP (polyvinyl pyrrolidone), and5.9 parts by weight of PVDF (polyvinylidene fluoride).

Comparative Example 7

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 55.9 parts by weight of activated carbon 1,31.5 parts by weight of lithium carbonate 1, 3.0 parts by weight ofKetjen black, 1.5 parts by weight of PVP (polyvinyl pyrrolidone), and8.1 parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 8

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 64.3 parts by weight of activated carbon 1,21.2 parts by weight of lithium carbonate 1, 3.5 parts by weight ofKetjen black, 1.7 parts by weight of PVP (polyvinyl pyrrolidone), and9.3 parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 9

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 70.8 parts by weight of activated carbon 1,13.3 parts by weight of lithium carbonate 1, 3.8 parts by weight ofKetjen black, 1.9 parts by weight of PVP (polyvinyl pyrrolidone), and10.2 parts by weight of PVDF (polyvinylidene fluoride) as well as amixed solvent of NMP (N-methylpyrrolidone) and pure water in a weightratio of 90:10, followed by dispersing the constituting substances toprepare the coating solution.

Comparative Example 10

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 35.6 parts by weight of activated carbon 1,56.4 parts by weight of lithium carbonate 1, 1.9 parts by weight ofKetjen black, 1.0 part by weight of PVP (polyvinyl pyrrolidone), and 5.1parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Comparative Example 11

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 10, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 38.9 parts by weight of activated carbon 1,52.4 parts by weight of lithium carbonate 1, 2.1 parts by weight ofKetjen black, 1.1 parts by weight of PVP (polyvinyl pyrrolidone), and5.6 parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

Example 13

A positive electrode precursor was prepared by using, with respect tothe composition of a coating solution of a positive electrode, 61.8parts by weight of activated carbon 1, 24.2 parts by weight of lithiumcarbonate 1, 3.3 parts by weight of Ketjen black, 1.7 parts by weight ofPVP (polyvinyl pyrrolidone), and 8.9 parts by weight of PVDF(polyvinylidene fluoride). At this time, the positive electrodeprecursor having a film thickness of the positive electrode activematerial layer of 153 μm was prepared by setting a clearance of theapplicator to 450 μm. Thereafter, a nonaqueous hybrid capacitor wasprepared in a similar manner as described in Example 1.

Example 14

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 13, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 57.8 parts by weight of activated carbon 1,29.2 parts by weight of lithium carbonate 1, 3.1 parts by weight ofKetjen black, 1.6 parts by weight of PVP (polyvinyl pyrrolidone), and8.3 parts by weight of PVDF (polyvinylidene fluoride).

Comparative Example 12

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 13, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 72.9 parts by weight of activated carbon 1,10.7 parts by weight of lithium carbonate 1, 3.9 parts by weight ofKetjen black, 2.0 parts by weight of PVP (polyvinyl pyrrolidone), and10.5 parts by weight of PVDF (polyvinylidene fluoride) as well as amixed solvent of NMP (N-methylpyrrolidone) and pure water in a weightratio of 90:10, followed by dispersing the constituting substances toprepare the coating solution.

Comparative Example 13

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 13, except for preparing a positive electrodeprecursor by using with respect to the composition of a coating solutionof a positive electrode, 77.2 parts by weight of activated carbon 1, 5.4parts by weight of lithium carbonate 1, 4.2 parts by weight of Ketjenblack, 2.1 parts by weight of PVP (polyvinyl pyrrolidone), and 11.1parts by weight of PVDF (polyvinylidene fluoride) as well as a mixedsolvent of NMP (N-methylpyrrolidone) and pure water in a weight ratio of90:10, followed by dispersing the constituting substances to prepare thecoating solution.

The evaluation results of the positive electrode precursors and those ofthe nonaqueous hybrid capacitors in Examples to 14 and ComparativeExamples 11 are shown in Table 1.

TABLE 1 A B C D E (g/m²) (g/m²) A/B (m²/cm²) C/

(μL/cm²) (μL/cm²)

 

Exp. 1 13.60

3.46

1.40 11.86 0.414 Exp. 2 8.54

3.63

0.87 1.47 11.97 0.402 Exp. 3 6.11

3.78

0.86

11.75 0.409 Exp. 4

0.700 3.53

0.85 1.41

0.416 Exp. 5

0.118 0.84 1.45

0.419 Com. 5.43

0.188 0.47 0.016

0.48

0.319 Exp. 1 Com. 4.73

0.167 0.49 0.017

0.45 7.61

Exp. 2 Com.

0.018

0.43 6.47

Exp. 3 Exp. 6 30.53 56.30

6.53 0.116

Exp. 7 34.60 56.93 0.608

1.68

Exp. 8

55.79

6.77

1.57

Exp. 9 13.31 56.13

6.89

1.69

Com.

56.34 0.173 0.97 0.017

0.88 17.65 0.313 Exp. 4 Com. 4.89 56.61 0.086 0.95 0.017

0.91 11.43

Exp. 5 Com.

56.11

0.89 0.016 0.49

8.89

Exp. 6 Exp. 10

0.57 4.41 0.436 Exp. 11 7.65 10.04

1.17 0.117 0.33 0.55 4.39 0.437 Exp. 12

0.980

0.118 0.31

4.35

Com. 4.75

0.460

3.41 0.330 Exp. 7 Com.

0.13

Exp. 8 Com. 1.56 10.19 0.153

0.11

1.41 0.138 Exp. 9 Com.

0.10

3.74 0.366 Exp. 10 Com 11.33 10.31 1.099

0.11

3.56 0.345 Exp. 11 Exp. 13

84.31

0.133

35.45

Exp. 14 34.97 84.87

10.87

0.415 Com.

85.61 0.119

0.018

1.35

Exp. 12 Com. 4.07

0.050

0.67

0.146 Exp. 13

indicates data missing or illegible when filed

Charging and discharging of the nonaqueous hybrid capacitor proceed bydecomposing the alkali metal compound contained in the positiveelectrode precursor, from which the alkali metal ions associating withcharging and discharging are pre-doped to the negative electrode orreleased in the electrolytic solution. When the alkali metal ions aresufficiently present in the negative electrode or the electrolyticsolution, the static capacitance, Fa of the nonaqueous hybrid capacitoris proportional to the weight, B of the positive electrode activematerial. Namely, the ratio of Fa/B, i.e., the ratio of the staticcapacitance, Fa of the nonaqueous hybrid capacitor to the weight, B ofthe positive electrode active material takes a certain fixed value,however, when decomposition of the alkali metal compound is incomplete,the alkali metal ions associating with charging and discharging aredeficient, thereby the value of Fa/B is decreased.

From Table 1, Fa/B is found to be a value of from 0.4 to 0.45, when0.20≤A/B≤1.00 as well as 1≤C≤20 is satisfied, from which a sufficientamount of the alkali metal ions is considered to be present in thenonaqueous hybrid capacitor. On the other hand, it is conjectured thatwhen at least either one of 0.20≤A/B≤1.00 or 1≤C≤20 is not satisfied,decomposition of the alkali metal compound is incomplete, thereby thevalue of Fa/B is decreased.

It is conjectured that when the coating solution of the positiveelectrode is dispersed, the alkali metal compound in the coatingsolution which dissolves in a trace amount by addition of about 1% ofpure water into NMP could stick to the surface of the activated carbonin a moderate amount. Therefore, it is considered that the alkali metalcompound in the pre-doping was decomposed efficiently, and thepre-doping was completed in a short period of only 2 hours. On the otherhand, it is conjectured that when the amount of pure water increases toabout 10%, an excessive amount of the alkali metal compound proceeds todissolve into the solution, from which impregnation of the electrolyticsolution becomes incomplete, since the surface and the side of theactivated carbon are converted with the alkali metal compound, therebydecomposition of the alkali metal compound was inhibited.

Example 15

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and sodium carbonate as the alkali metal compound.

Example 16

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and potassium carbonate as the alkali metal compound.

Example 17

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and sodium carbonatein a weight ratio of 9:1 as the alkali metal compound.

Example 18

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium 5 carbonate and sodiumcarbonate in a weight ratio of 1:1 as the alkali metal compound.

Example 19

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium 10 carbonate and sodiumcarbonate in a weight ratio of 1:9 as the alkali metal compound.

Example 20

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and potassiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 21

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and rubidiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 22

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and cesium carbonatein a weight ratio of 9:1 as the alkali metal compound.

Example 23

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate, sodium carbonateand potassium carbonate in a weight ratio of 9:0.5:0.5 as the alkalimetal compound.

Comparative Example 14

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 15, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 15

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 16, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 16

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 17, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 17

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 18, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 18

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 19, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 19

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 20, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 20

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 21, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 21

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 22, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 22

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 23, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Example 24

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and sodium carbonatein a weight ratio of 9:1 as the alkali metal compound.

Example 25

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 6, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and potassiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Comparative Example 23

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 5, except for using activated carbon 2as the activated carbon and a mixture of lithium carbonate and sodiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Comparative Example 24

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 5, except for using activated carbon 2as the activated carbon and a mixture of lithium carbonate and potassiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 26

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and sodium oxide ina weight ratio of 9:1 as the alkali metal compound.

Example 27

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and potassiumhydroxide in a weight ratio of 1:1 as the alkali metal compound.

Example 28

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and sodium chloridein a weight ratio of 9:1 as the alkali metal compound.

Example 29

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 1, except for using activated carbon 2 as theactivated carbon and a mixture of lithium carbonate and potassiumfluoride in a weight ratio of 9:1 as the alkali metal compound.

The evaluation results of positive electrode precursors and those ofnonaqueous hybrid capacitors in Examples 15 to 29 and ComparativeExamples 14 to 24 are shown in Table 2.

TABLE 2 Alkali metal carbonate Formulation C(m²/ D(μL/ E(μL/ Mixtureratio A(g/m²) B(g/m²) A/B cm²) C/B cm²) cm²) Fa(F) Fa/B Exp. 15 Na₂CO₃ 113.60 28.43 0.478 8.06 0.284 1.76 3.34 14.42 0.507 Exp. 16 K₂CO₃ 1 13.3228.73 0.464 8.97 0.312 1.86 3.65 14.12 0.491 Exp. 17 Li₂CO₃ Na₂CO₃ 9:113.54 28.12 0.482 7.79 0.277 1.82 3.42 15.31 0.544 Exp. 18 Li₂CO₃ Na₂CO₃1:1 13.57 29.02 0.468 8.68 0.299 1.85 3.54 15.11 0.521 Exp. 19 Li₂CO₃Na₂CO₃ 1:9 13.25 29.21 0.454 8.39 0.287 1.82 3.59 14.88 0.509 Exp. 20Li₂CO₃ K₂CO₃ 9:1 13.75 28.81 0.477 8.65 0.300 1.72 3.41 15.19 0.527 Exp.21 Li₂CO₃ Rb₂CO₃ 9:1 13.83 28.53 0.485 8.06 0.283 1.91 3.37 15.01 0.526Exp. 22 Li₂CO₃ Cs₂CO₃ 9:1 13.42 28.12 0.477 8.18 0.291 1.90 3.32 14.850.528 Exp. 23 Li₂CO₃ Na₂CO₃ K₂CO₃ 9:0.5:0.5   13.58 28.43 0.478 8.360.294 1.88 3.51 15.34 0.540 Com. Exp. 14 Na₂CO₃ 1 13.68 28.94 0.473 0.510.018 0.24 0.47 10.52 0.364 Com. Exp. 15 K₂CO₃ 1 13.49 28.74 0.474 0.480.017 0.26 0.51 10.11 0.356 Com. Exp. 16 Li₂CO₃ Na₂CO₃ 9:1 13.38 29.030.461 0.52 0.018 0.27 0.49 10.32 0.355 Com. Exp. 17 Li₂CO₃ Na₂CO₃ 1:113.75 28.65 0.480 0.49 0.017 0.25 0.53 10.05 0.351 Com. Exp. 18 Li₂CO₃Na₂CO₃ 1:9 13.18 28.87 0.457 0.50 0.017 0.28 0.56 9.85 0.341 Com. Exp.19 Li₂CO₃ K₂CO₃ 9:1 13.86 28.45 0.487 0.46 0.016 0.23 0.49 10.09 0.355Com. Exp. 20 Li₂CO₃ Rb₂CO₃ 9:1 13.49 28.41 0.475 0.48 0.017 0.24 0.479.94 0.350 Com. Exp. 21 Li₂CO₃ Cs₂CO₃ 9:1 13.33 29.11 0.458 0.53 0.0180.21 0.49 9.68 0.333 Com. Exp. 22 Li₂CO₃ Na₂CO₃ K₂CO₃ 9:0.5:0.5   13.5828.94 0.469 0.51 0.018 0.25 0.51 10.51 0.363 Exp. 24 Li₂CO₃ Na₂CO₃ 9:130.21 56.74 0.532 16.45 0.290 4.07 7.31 29.21 0.515 Exp. 25 Li₂CO₃ K₂CO₃9:1 30.98 56.12 0.552 17.43 0.311 3.91 7.16 29.84 0.532 Com. Exp. 23Li₂CO₃ Na₂CO₃ 9:1 29.78 56.18 0.530 0.91 0.016 0.41 0.81 20.31 0.362Com. Exp. 24 Li₂CO₃ K₂CO₃ 9:1 30.56 56.35 0.542 0.87 0.015 0.42 0.8419.56 0.347 Exp. 26 Li₂CO₃ Na₂O 9:1 13.42 28.76 0.467 8.16 0.284 1.933.41 15.31 0.532 Exp. 27 Li₂CO₃ KOH 9:1 13.55 28.13 0.482 8.31 0.2951.79 3.57 15.11 0.537 Exp. 28 Li₂CO₃ NaCl 9:1 13.28 28.63 0.464 8.520.298 1.81 3.51 15.09 0.527 Exp. 29 Li₂CO₃ KF 9:1 13.72 28.49 0.482 8.220.289 1.95 3.55 15.27 0.536

From Table 2, even in the case the different activated carbon and thedifferent alkali metal compound are used, Fa/B shows the maximum value,when 0.20≤A/B≤1.00 and 1≤C≤20 are satisfied. By considering the result,a sufficient amount of the alkali metal ions is considered to be presentin the nonaqueous hybrid capacitor.

Next, a detailed explanation on the embodiments in the second aspect ofthe present invention will be given below.

Example 30 <Crushing of Lithium Carbonate>

Lithium carbonate 2 having an average particle diameter of 0.4 μm wasobtained by allowing 20 g of lithium carbonate having an averageparticle diameter of 53 μm to stand under an environment of atemperature of 60° C. and humidity of 80% RH for 2 hours, cooling it to−20° C. in a rotation and revolution-type crushing machine (NP-100),manufactured by Thinky Co., Ltd., and crushing it in the machine withzirconia beads having a diameter of 1.0 mm under 1700 rpm for 20minutes.

<Production of Positive Electrode Precursor>

A positive electrode precursor was produced as follows using activatedcarbon 1 as the positive electrode active material and lithium carbonate2 as the alkali metal compound.

A coating solution was obtained by mixing 55.5 parts by weight ofactivated carbon 1, 32.0 parts by weight of lithium carbonate, 3.0 partsby weight of ketjen black, 1.5 parts by weight of PVP (polyvinylpyrrolidone), and 8.0 parts by weight of PVDF (polyvinylidene fluoride)as well as a mixed solvent of NMP (N-methylpyrrolidone) and pure waterin a weight ratio of 99:1, followed by dispersing them using a thin filmspin-type high speed mixer, Filmix, manufactured by PRIMIX Co., Ltd.under the condition of a peripheral speed of 17 m/s.

The viscosity (ηb) and the value, TI of the resulting coating solutionwere measured using an E-type viscometer, TVE-35H, manufactured by ToukiSangyo Co., Ltd. As a result, the viscosity (ηb) was 2,490 mPa·s, andthe value, TI 4.2. Dispersity of the resulting coating solution wasmeasured using a particle gauge, manufactured by YOSHIMITSU SEIKI Co.,Ltd. and the particle size was 31 μm.

Positive electrode precursor 2 was obtained by setting a clearance ofthe applicator of an automatic coating apparatus, manufactured by TESTERSANGYO Co., Ltd. to 150 μm, and coating the coating solution on onesurface of an aluminum foil having a thickness of 15 μm under thecondition of a coating speed of 1 m/min. Resulting positive electrodeprecursor 2 was subjected to press rolling by using a roll-press machineunder the conditions of a pressure of 6 kN/cm and a surface temperatureat the pressing part of 25° C. A film thickness of the positiveelectrode active material layer of resulting positive electrodeprecursor 2 was determined by subtracting the thickness of the aluminumfoil from the average value of thicknesses of the precursor measured atarbitrary 10 points by using a film thickness meter, Linear GaugeSensor, GS-551, manufactured by ONO SOKKI Co., Ltd. As a result, thefilm thickness of the positive electrode active material layer was 49μm.

<Calculation of X>

Sample 3 was prepared by cutting positive electrode precursor 2 in asize of 10 cm×5 cm, and weighing M₀ thereof to be 0.3076 g. Lithiumcarbonate in sample 3 was eluted in distilled water by impregnatingsample 1 in 31.0 g of distilled water, followed by holding it until theelapse of 3 days in an environment at 25° C. Then sample 3 was takenout, and vacuum dried for 12 hours under conditions of 150° C. and 3kPa. The weight, M₁ of the sample at this time was 0.2411 g. After this,the active material layer on the positive electrode power collector wasremoved using a spatula and a brush, and then the weight M₂ of thepositive electrode power collector was measured to be 0.0990 g.According to equation (5), X was calculated to be 31.9% by weight.

<Calculation of S₁, S₂>

[Preparation of Sample]

A small piece having a size of 1 cm×1 cm was cut out from positiveelectrode precursor 2, and the surface thereof was coated by sputteringgold under a vacuum of 10 Pa.

[Measurement of Surface SEM and EDX]

The surface of the positive electrode prepared above which was exposedto an atmospheric environment was analyzed by SEM and EDX. Themeasurement conditions are described below.

(Measurement Conditions of SEM-EDX)

Measurement apparatus: Field emission-type SEM, FE-SEM, S-4700,manufactured by Hitachi High-Technologies Corp., and energydispersion-type X-ray analysis apparatus, E MAX, manufactured by Horiba,Co., Ltd.

Acceleration voltage: 10 kV

Emission current: 10 μA

Measurement magnification: 2000 times

Electron beam incident angle: 90°

X-ray take out angle: 30°

Dead time: 15%

Mapping elements: C, O, F

Measurement pixel number: 256×256 pixels

Measurement time: 60 sec.

Integration number: 50 times

Brightness and contrast were adjusted so that there were no pixelsshowing the maximum brightness value, and an average value of brightnessvalue fell within a range of 40% to 60% of the maximum brightness value.

(Analysis of SEM-EDX)

In the oxygen mapping, the images obtained were binarized based on theaverage value of luminance values by using image analysis software(ImageJ). Area S₁ of oxygen obtained in the oxygen mapping this time was25.6% with respect to the total images.

[Measurement of Cross-Section SEM and EDX]

A cross section perpendicular to the surface direction of positiveelectrode precursor 2 was prepared by cutting out from positiveelectrode precursor 2 in a size of 1 cm×1 cm, using SM-09020CP,manufactured by JEOL in an argon gas atmosphere under the conditions ofan acceleration voltage of 4 kV and a beam diameter of 500 μm. Afterthis, the cross-section SEM and EDX were measured by the methoddescribed above.

In the cross-section SEM and EDX of the resulting positive electrodeprecursor, the images obtained in the oxygen mapping and fluorinemapping were binarized in a similar manner described above. The area S₂of oxygen obtained in the oxygen mapping this time was 24.5% withrespect to the total images.

From the measurement results of SEM-EDX, the following calculationresults were obtained: S₁/X=0.80, and S₂/X=0.77.

[Preparation of Nonaqueous Hybrid Capacitor]

One sheet of positive electrode precursor 2 in which the positiveelectrode active material layer has a size of 10.0 cm×5.0 cm, and onesheet of negative electrode 1 in which the negative electrode activematerial layer has a size of 10.1 cm×5.1 cm were cut out respectively,and also one sheet of a separator made of polyethylene and having a sizeof 10.3 cm×5.3 cm (manufactured by Asahi Kasei, Corp., thickness 15 μm)was prepared. An electrode laminated body was obtained by laminatingthem in the order of positive electrode precursor 2, the separator, andnegative electrode 1.

After the resulting electrode laminated body was connected to a positiveelectrode terminal and a negative electrode terminal by ultrasonicwelding, the body was put into a container fabricated by an aluminumlaminate packaging material, and then, three sides of the containerincluding the side with the two electrode terminals were heat-sealed.The nonaqueous hybrid capacitor was prepared by pouring 3.5 g of apropylene carbonate (PC) solution of LiPF₆ having a concentration of anelectrolyte of 1.2 M as a nonaqueous electrolytic solution under anatmospheric pressure at 25° C. into the electrode laminated bodyaccommodated in the aluminum laminate packaging material in a dry airenvironment having a dew point of −40° C. or lower. Subsequently, thenonaqueous hybrid capacitor was introduced to a pressure reductionchamber, and a pressure inside the chamber was reduced from anatmospheric pressure to −87 kPa, and returned to an atmosphericpressure. After this, the capacitor was allowed to stand for 5 minutes.Then, a step of returning to an atmospheric pressure after reducing thepressure from an atmospheric pressure to −87 kPa was repeated fourtimes, followed by allowing the capacitor to stand for 15 minutes.Furthermore, after the pressure was reduced from an atmospheric pressureto −91 kPa, it was returned to an atmospheric pressure. Similarly, thestep of reducing the pressure and returning to an atmospheric pressurewas repeated seven times in total (each pressure was reduced to −95,−96, −97, −81, −97, −97, and −97 kPa, respectively). The nonaqueouselectrolytic solution was impregnated to the electrode laminated body bythe above steps.

After this, the nonaqueous hybrid capacitor was put in areduced-pressure sealing machine in which the pressure was in a state ofa reduced pressure of −95 kPa, and the aluminum laminate packagingmaterial was encapsulated by applying pressure of 0.1 MPa at 180° C. for10 seconds.

[Pre-Doping Step]

The resulting nonaqueous hybrid capacitor was put into an argon boxhaving a temperature of 25° C., dew point−60° C., and an oxygenconcentration of 1 ppm. Doping of lithium to the negative electrode wascarried out by unsealing the aluminum laminate packaging materialaccommodating the nonaqueous hybrid capacitor, cutting out a surplusportion of the packaging material, carrying out charging up to 4.5 Vunder the constant current of 50 mA, and subsequently initial chargingunder the constant voltage at 4.5 V for 2 consecutive hours using apower source (P4LT18-0.2), manufactured by Matsusada Precision Inc.After completion of the lithium doping, the aluminum laminate wasencapsulated using a heat seal machine (FA-300), manufactured byFUJIIMPULSE Co., Ltd.

[Aging Step]

The nonaqueous hybrid capacitor after the lithium doping was taken outfrom the argon box, and then, after carrying out constant currentdischarging down to 3.8 V under the current of 50 mA at 25° C., avoltage was adjusted to 3.8 V by carrying out constant voltagedischarging under the voltage at 3.8 V for 1 hour. Subsequently, thenonaqueous hybrid capacitor was stored in a thermostat chamber at 60° C.for 8 hours.

[Gas Venting Step]

After aging, a part of the aluminum laminate packaging materialaccommodating the nonaqueous hybrid capacitor was unsealed at atemperature of 25° C. under a dry air environment having a dew point of−40° C. or lower. Subsequently, the nonaqueous hybrid capacitor was putin a pressure reduction chamber, and the step was repeated three timesin total, in which the pressure was reduced from an atmospheric pressureto −80 kPa over a period of 3 minutes, and returned to an atmosphericpressure over a period of 3 minutes by using a diaphragm pump(manufactured by KNF Co., Ltd., N816. 3KT. 45. 18). Then, after puttingthe nonaqueous hybrid capacitor in a reduced-pressure sealing machine toreduce pressure to −90 kPa, the aluminum laminate packaging material wasencapsulated by sealing under a pressure of 0.1 MPa at 200° C. for 10seconds.

[Evaluation of Nonaqueous Hybrid Capacitor] [Measurement of StaticCapacitance Fa]

The nonaqueous hybrid capacitor obtained in the previous step wassubjected to constant current charging in a thermostat chamber set at25° C. up to 3.8 V under the current of 2C (10 mA), and subsequentlyconstant voltage charging by applying the voltage of 3.8 V for 30minutes in total. After this, constant current discharging was carriedout down to 2.2 V under the current of 2C (10 mA), and the capacitanceso obtained is defined as Q(C). The static capacitance, Fa calculated byF=Q/(3.8−2.2) was 11.52 F.

Example 31

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent of for thepositive electrode coating solution.

Example 32

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3 as a dispersing solvent for the positiveelectrode coating solution.

Example 33

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using with respect to thecomposition of the positive electrode coating solution, 64.4 parts byweight of activated carbon 1, 21.1 parts by weight of lithium carbonate2, 3.5 parts by weight of Ketjen black, 1.7 parts by weight of PVP(polyvinyl pyrrolidone), and 9.3 parts by weight of PVDF (polyvinylidenefluoride).

Example 34

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 33, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent for the positiveelectrode coating solution.

Example 35

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 33, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3 as a dispersing solvent for the positiveelectrode coating solution.

Example 36

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using with respect to the composition of the positiveelectrode coating solution, 71.7 parts by weight of activated carbon 1,12.2 parts by weight of lithium carbonate 2, 3.9 parts by weight ofKetjen black, 1.9 parts by weight of PVP (polyvinyl pyrrolidone), and10.3 parts by weight of PVDF (polyvinylidene fluoride).

Example 37

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 36, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent for the positiveelectrode coating solution.

Example 38

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 36, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3 as a dispersing solvent of a coatingsolution for the positive electrode.

Example 39

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using with respect to the composition of the positiveelectrode coating solution, 74.4 parts by weight of activated carbon 1,8.8 parts by weight of lithium carbonate 2, 4.0 parts by weight ofKetjen black, 2.0 parts by weight of PVP (polyvinyl pyrrolidone), and10.7 parts by weight of PVDF (polyvinylidene fluoride).

Example 40

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 39, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent for the positiveelectrode coating solution.

Example 41

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 39, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3 as a dispersing solvent for the positiveelectrode coating solution.

Example 42

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using with respect to the composition of the positiveelectrode coating solution, 76.5 parts by weight of activated carbon 1,6.3 parts by weight of lithium carbonate 2, 4.1 parts by weight ofKetjen black, 2.1 parts by weight of PVP (polyvinyl pyrrolidone), and11.0 parts by weight of PVDF (polyvinylidene fluoride).

Example 43

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 42, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent for the positiveelectrode coating solution.

Example 44

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 42, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3 as a dispersing solvent for the positiveelectrode coating solution.

Example 45

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for preparing a positive electrodeprecursor using with respect to the composition of the positiveelectrode coating solution, 43.1 parts by weight of activated carbon 1,47.2 parts by weight of lithium carbonate 2, 2.3 parts by weight ofKetjen black, 1.2 parts by weights of PVP (polyvinyl pyrrolidone), and6.2 parts by weight of PVDF (polyvinylidene fluoride).

Example 46

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 45, except for preparing the positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 98:2 as a dispersing solvent for the positiveelectrode coating solution.

Example 47

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 45, except for preparing a positive electrodeprecursor using a mixed solvent of NMP (N-methylpyrrolidone) and purewater in a weight ratio of 97:3, as a dispersing solvent for thepositive electrode coating solution.

Comparative Example 26

Lithium carbonate 3 having an average particle diameter of 1.5 μm wasobtained by crushing 20 g of lithium carbonate having an averageparticle diameter of 53 μm with zirconia beads having a diameter of 0.1mm by using a rotation and revolution-type crushing machine (NP-100),manufactured by Thinky Corp. at 1,700 rpm for 20 minutes in anenvironment of 25° C.

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 30, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution, 78.5 parts by weight of activatedcarbon 1, 3.8 parts by weight of lithium carbonate 3, 4.2 parts byweight of Ketjen black, 2.1 parts by weight of PVP (polyvinylpyrrolidone), and 11.3 parts by weight of PVDF (polyvinylidene fluoride)as well as NMP (N-methylpyrrolidone) as a dispersing solvent.

Comparative Example 27

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 99.9:0.1 as a dispersing solvent forthe positive electrode coating solution.

Comparative Example 28

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution, 76.5 parts by weight of activatedcarbon 1, 6.3 parts by weight of lithium carbonate 3, 4.1 parts byweight of Ketjen black, 2.1 parts by weight of PVP (polyvinylpyrrolidone), and 11.0 parts by weight of PVDF (polyvinylidene fluoride)as well as NMP (N-methylpyrrolidone) as a dispersing solvent.

Comparative Example 29

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 28, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 99.9:0.1 as a dispersing solvent forthe positive electrode coating solution.

Comparative Example 30

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution, 71.7 parts by weight of activatedcarbon 1, 12.2 parts by weight of lithium carbonate 3, 3.9 parts byweight of Ketjen black, 1.9 parts by weight of PVP (polyvinylpyrrolidone), and 10.3 parts by weight of PVDF (polyvinylidene fluoride)as well as NMP (N-methylpyrrolidone) as a dispersing solvent.

Comparative Example 31

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 30, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 99.9:0.1 as a dispersing solvent forthe positive electrode coating solution.

Comparative Example 32

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution, 64.4 parts by weight of activatedcarbon 1, 21.1 parts by weight of lithium carbonate 3, 3.5 parts byweight of Ketjen black, 1.7 parts by weight of PVP (polyvinylpyrrolidone), and 9.3 parts by weight of PVDF (polyvinylidene fluoride)as well as a mixed solvent of NMP (N-methylpyrrolidone) and pure waterin a weight ratio of 90:10 as a dispersing solvent.

Comparative Example 33

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 32, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 80:20 as a dispersing solvent forthe positive electrode coating solution.

Comparative Example 34

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution, 55.6 parts by weight of activatedcarbon 1, 31.9 parts by weight of lithium carbonate 3, 3.0 parts byweight of Ketjen black, 1.5 parts by weight of PVP (polyvinylpyrrolidone), and 8.0 parts by weight of PVDF (polyvinylidene fluoride)as well as a mixed solvent of NMP (N-methylpyrrolidone) and pure waterin a weight ratio of 90:10 as a dispersing solvent.

Comparative Example 35

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 34, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 80:20 as a dispersing solvent forthe positive electrode coating solution.

Comparative Example 36

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 26, except for preparing a positiveelectrode precursor using with respect to the composition of thepositive electrode coating solution a coating solution of a positiveelectrode, 30.8 parts by weight of activated carbon 1, 62.3 parts byweight of lithium carbonate 3, 1.7 parts by weight of Ketjen black, 0.8part by weight of PVP (polyvinyl pyrrolidone), and 4.4 parts by weightof PVDF (polyvinylidene fluoride) as well as a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent.

Comparative Example 37

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Comparative Example 36, except for preparing a positiveelectrode precursor using a mixed solvent of NMP (N-methylpyrrolidone)and pure water in a weight ratio of 80:20 as a dispersing solvent forthe positive electrode coating solution.

The evaluation results of positive electrode precursors and those ofnonaqueous hybrid capacitors in Examples 30 to 47 and ComparativeExamples 26 to 37 are shown in Table 3.

TABLE 3

/X

/X

  Exp. 30

Exp. 31

Exp. 32

Exp. 33

Exp. 34

Exp. 35

Exp. 36

Exp. 37

Exp. 38

Exp. 39

Exp. 40

Exp. 41

Exp. 42

Exp. 43

Exp. 44

Exp. 45

Exp. 46

Exp. 47

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

Com.

Exp.

indicates data missing or illegible when filed

As explained about the present embodiments above, charging anddischarging of the nonaqueous hybrid capacitor proceed by decomposingthe alkali metal compound contained in the positive electrode precursor,from which the alkali metal ions associating with charging anddischarging are pre-doped to the negative electrode or released in theelectrolytic solution.

From Table 3, it has been understood that the capacitance of thenonaqueous hybrid capacitor takes the maximum value, when 5≤X≤50,5≤S₁≤60, and 0.50≤S₁/X≤2.00 are all satisfied. The reason is conjecturedas follows: When X is below 5, the static capacitance Fa decreases,because the concentration of the alkali metal ions associated withcharging and discharging are deficient; when X is larger than 60, thepre-doping rate is decreased, because the excessive amount of the alkalimetal compound covers the surface of the active material; when S₁ isless than 5 or S₁/X is less than 0.50, the reaction overvoltage in thepre-doping increases, because the electric conduction between thepositive electrode active material and the alkali metal compound isinsufficient; when S₁ is larger than 60 or S₁/X is larger than 2.00, theexcessive amount of the alkali metal compound covers the surface of thepositive electrode active material, from which diffusion of the alkalimetal ions generated by decomposition of the alkali metal compound intothe electrolytic solution is inhibited, thereby the pre-doping rate isdecreased.

It is conjectured that when the coating solution for the positiveelectrode is dispersed, the alkali metal compound in the coatingsolution which dissolves in a trace amount by addition of a trace amountof pure water into NMP could stick to the surface of the activatedcarbon in a moderate amount. Therefore, it is considered that the alkalimetal compound in the pre-doping was decomposed efficiently, and thepre-doping was completed in a short period of only 2 hours. On the otherhand, it is conjectured that when the amount of pure water increases toabout 10%, an excessive amount of the alkali metal compound proceeds todissolve into the solution, from which impregnation of the electrolyticsolution became incomplete, since the surface and the side of theactivated carbon are converted with the alkali metal compound, therebydecomposition of the alkali metal compound was inhibited.

Example 48

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon and sodium carbonate as the alkali metal compound.

Example 49

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon and potassium carbonate as the alkali metal compound.

Example 50

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and sodiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 51

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and sodiumcarbonate in a weight ratio of 1:1 as the alkali metal compound.

Example 52

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and sodiumcarbonate in a weight ratio of 1:9 as the alkali metal compound.

Example 53

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and potassiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 54

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and rubidiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 55

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate and cesiumcarbonate in a weight ratio of 9:1 as the alkali metal compound.

Example 56

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and a mixture of lithium carbonate, sodium carbonate,and potassium carbonate in a weight ratio of 9:0.5:0.5 as the alkalimetal compound.

Comparative Example 38

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 48, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 39

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 49, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 40

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 50, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 41

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 51, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 42

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 52, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 43

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 53, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 44

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 54, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 45

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 55, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Comparative Example 46

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 56, except for using a mixed solvent of NMP(N-methylpyrrolidone) and pure water in a weight ratio of 90:10 as adispersing solvent for the positive electrode coating solution.

Example 57

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and replacing the alkali metal compound with a mixtureof lithium carbonate and sodium oxide in a weight ratio of 9:1.

Example 58

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and replacing the alkali metal compound with a mixtureof lithium carbonate and potassium hydroxide in a weight ratio of 9:1.

Example 59

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and replacing the alkali metal compound with a mixtureof lithium carbonate and sodium chloride in a weight ratio of 9:1.

Example 60

A nonaqueous hybrid capacitor was prepared in a similar manner asdescribed in Example 30, except for using activated carbon 2 as theactivated carbon, and replacing the alkali metal compound with a mixtureof lithium carbonate and potassium fluoride in a weight ratio of 9:1.

The evaluation results of positive electrode precursors and those ofnonaqueous hybrid capacitors in Examples 48 to 60 and ComparativeExamples 38 to 46 are shown in Table 4.

TABLE 4 Alkali metal carbonate Formulation X (% by S₁ S₂ Mixture ratiomass (%) S₁/X (%) S₂/X Fa(F) Exp. 48 Na₂CO₃ 1 31.9 23.6 0.74 22.5 0.7111.65 Exp. 49 K₂CO₃ 1 32.0 23.1 0.72 22.8 0.71 11.72 Exp. 50 Li₂CO₃Na₂CO₃ 9:1 32.1 24.2 0.75 23.1 0.72 11.83 Exp. 51 Li₂CO₃ Na₂CO₃ 1:1 32.224.4 0.76 23.1 0.72 11.52 Exp. 52 Li₂CO₃ Na₂CO₃ 1:9 32.0 25.1 0.78 22.50.70 11.24 Exp. 53 Li₂CO₃ K₂CO₃ 9:1 32.0 24.9 0.78 21.0 0.66 11.58 Exp.54 Li₂CO₃ Rb₂CO₃ 9:1 32.1 25.8 0.80 23.1 0.72 11.32 Exp. 55 Li₂CO₃Cs₂CO₃ 9:1 31.9 22.5 0.71 20.7 0.65 11.21 Exp. 56 Li₂CO₃ Na₂CO₃ K₂CO₃9:0.5:0.5   32.0 26.1 0.82 24.7 0.77 11.68 Com. Exp. 38 Na₂CO₃ 1 32.167.2 2.09 65.9 2.05 8.65 Com. Exp. 39 K₂CO₃ 1 32.0 66.8 2.09 64.9 2.038.53 Com. Exp. 40 Li₂CO₃ Na₂CO₃ 9:1 32.1 69.8 21.7 68.3 2.13 9.02 Com.Exp. 41 Li₂CO₃ Na₂CO₃ 1:1 32.0 68.6 2.14 67.1 2.10 8.95 Com. Exp. 42Li₂CO₃ Na₂CO₃ 1:9 32.1 67.8 2.11 64.8 2.02 8.91 Com. Exp. 43 Li₂CO₃K₂CO₃ 9:1 31.9 69.5 2.18 65.8 2.06 9.11 Com. Exp. 44 Li₂CO₃ Rb₂CO₃ 9:131.9 67.8 2.13 65.1 2.04 9.04 Com. Exp. 45 Li₂CO₃ Cs₂CO₃ 9:1 32.1 69.52.17 67.4 2.10 8.76 Com. Exp. 46 Li₂CO₃ Na₂CO₃ K₂CO₃ 9:0.5:0.5   32.068.1 2.13 67.1 2.10 8.97 Exp. 57 Li₂CO₃ Na₂O 9:1 32.0 26.4 0.83 23.10.72 11.63 Exp. 58 Li₂CO₃ KOH 9:1 32.1 27.8 0.87 25.8 0.80 11.52 Exp. 59Li₂CO₃ NaCl 9:1 32.0 25.3 0.79 22.1 0.69 11.49 Exp. 60 Li₂CO₃ KF 9:132.0 22.1 0.69 20.6 0.64 11.31

In Table 4, even in the case that the different activated carbon and thedifferent alkali metal compound are used, the static capacitance, Faexhibits the maximum value, when 5≤X≤50, 5≤S₁≤60, and 0.50≤S₁/X≤2.00 areall satisfied, probably because a sufficient amount of the alkali metalions are present in the nonaqueous electrolytic solution and thenegative electrode of the nonaqueous hybrid capacitor.

A detailed explanation on the embodiments in the third aspect of thepresent invention will be given below.

Example 61 [Preparation of Positive Electrode Precursor]

A slurry for a positive electrode having a solid concentration of 14% byweight was obtained by mixing 63.5 parts by weight of commercialacetylene black (produced by Denka Co., Ltd.) as the positive electrodeactive material, 26.5 parts by weight of lithium carbonate having anaverage particle diameter of 3.0 μm as the lithium compound, 10.0 partsby weight of PTFE (polytetrafluoroethylene), and NMP(N-methylpyrrolidone). The positive electrode precursor was obtained bycoating the resulting slurry on one surface of an aluminum foil having athickness of 15 μm which is used as the positive electrode powercollector, drying, and pressing it. The thickness of the positiveelectrode active material layer in the resulting positive electrodeprecursor was 36 μm. The film thickness of the positive electrode activematerial layer is a value determined by subtracting the thickness of thepower collector from the average value of thicknesses of the positiveelectrode precursor measured at arbitrary 10 points of the precursor byusing a film thickness meter (Linear Gauge Sensor, GS-551), manufacturedby ONO SOKKI Co., Ltd. The amount, A₁ of lithium oxide per unit area ofthe positive electrode precursor was 8.5 g/m², and A₁/B₁ was 0.036.

[Preparation of Negative Electrode]

A slurry for a negative electrode was obtained by mixing 85.4 parts byweight of commercially available hard carbon (produced by Kureha Corp.),8.3 parts by weight of acetylene black, 6.3 parts by weight of PVdF(polyvinylidene fluoride), and NMP (N-methylpyrrolidone). The negativeelectrode was obtained by coating the resulting slurry on one surface ofan electrolytic copper foil having a thickness of 10 μm which is used asthe negative electrode power collector, drying, and pressing it. Thethickness of the negative electrode active material layer in theresulting negative electrode was measured in similar manner to that ofthe positive electrode active material layer, and was found to be 28 μm.

[Measurement of Capacitance Per Unit Weight of Negative Electrode]

By using the resulting negative electrode cut out in a size of 1.4cm×2.0 cm (2.8 cm²) as an operating electrode, metal lithium used as acounter electrode and a reference electrode, respectively, and thenonaqueous solution as an electrolytic solution in which LiPF₆ wasdissolved in propylene carbonate (PC) at a concentration of 1.0 mol/L,an electrochemical cell was prepared in an argon box.

For the resulting electrochemical cell, an initial charging capacitancewas measured by the following procedure by using a charging anddischarging apparatus (TOSCAT-3100U), manufactured by Toyosystem Corp.

For the electrochemical cell obtained, charging under the constantcurrent of 0.5 mA/cm² was carried out up to 0.01 V at a temperature of25° C., and further charging under the constant voltage was carried outdown to the current value of 0.01 mA/cm². The charging capacitance forthis charging under the constant current as well as charging under theconstant voltage, which was evaluated as the initial chargingcapacitance was 1.6 mAh, and the capacitance, G₁ per unit area of thenegative electrode was 5.7 Ah/m²

[Preparation of Nonaqueous Hybrid Capacitor]

Each sheet of the positive electrode precursor and the negativeelectrode, both of which were prepared above was cut out to a size of1.4 cm×2.0 cm (2.8 cm²), respectively. In addition, one sheet of aseparator made of polyethylene (manufactured by ASAHI KASEI E-materialsCorp., thickness 20 μm) was prepared. An electrode laminated body wasfabricated by laminating them in the order of the positive electrodeprecursor, the separator, and the negative electrode. In this electrodelaminated body, A₁ was 8.5 g/m², G₁ 5.7 Ah/m², and thus, the value ofA₁/G₁ was 1.49 g/Ah, all of which have been confirmed to satisfyrequirement of the present invention.

An electrochemical cell was prepared by putting this laminated body anda stainless steel foil adhered with a metal lithium foil as a referenceelectrode to a container fabricated with an aluminum laminate filmcomposed of polypropylene and an aluminum foil, and pouring theelectrolytic solution to the container in which LiPF₆ was dissolved inpropylene carbonate (PC) at a concentration of 1.0 mol/l.

(Voltage Applying Step (Pre-Doping Step))

The nonaqueous hybrid capacitor of Example 61 was prepared by carryingout for the resulting electrochemical cell an initial charging by amethod of the constant current charging up to 5.0 V under the currentvalue of 0.1 mA at an environment of 25° C., subsequently charging underthe constant voltage at 5.0 V for 72 hours by using a charging anddischarging apparatus (TOSCAT-3100U), manufactured by Toyosystem Corp.,and pre-doping lithium ions to the negative electrode. The chargingcurves (the current value, the voltage change, the positive electrodepotential change, and the negative electrode potential change) in thiscase are shown in FIG. 1.

Then, it has been confirmed by disassembling the nonaqueous hybridcapacitor prepared in the argon box that metal lithium did not depositon the negative electrode surface.

Comparative Example 47

In [Preparation of positive electrode precursor] of the Example 61, aslurry for a positive electrode was prepared in a similar manner asdescribed in Example 61 except for changing the amount of acetyleneblack to 90.0 parts by weight, and not using the alkali metal compound.By using the slurry, a positive electrode precursor having the positiveelectrode active material layer having a thickness of 34 μm wasobtained. Then an electrochemical cell was fabricated, and evaluated bythe similar method as described in Example 61 except for using theresulting positive electrode precursor. The charging curves at theinitial charging are shown in FIG. 2.

<Evaluation of Voltage Applying Step (Pre-Doping Step) (Comparison ofExample 61 and Comparative Example 47)>

In Comparative Example 47 (FIG. 2), an electric current of about 6 mAh/gflowed at the very initial period of charging, however, the reaction wasfinished just after this period. It is considered that the electriccurrent flown at the initial period was generated by pre-doping oflithium ions in the electrolytic solution to the negative electrode, andthe electric current was not flown after the electrolytes in theelectrolytic solution were completely consumed.

On the other hand, in Example 61 (FIG. 1), the electric current of 264mAh/g flowed, that was over the equivalent amount (6 mAh/g) of theelectrolytes in the electrolytic solution. At the same time, byobserving that the negative electrode potential dropped down to 0.2 V, asufficient amount of lithium ions was confirmed to be pre-doped to thenegative electrode. In Example 61, it is considered that by oxidativedecomposition of the alkali metal compound in the positive electrodeprecursor at the initial charging period, followed by reduction of thusgenerated lithium ions at the negative electrode, therefore lithium ionswere pre-doped to the negative electrode.

Example 62 [Preparation of Positive Electrode Precursor]

A carbide having an average particle diameter of 7 μm was obtained bycarrying out carbonization treatment of a phenol resin in a furnace at600° C. for 2 hours under a nitrogen atmosphere, crushing it using aball mill, and carrying out its classification. Activation was carriedout by mixing this carbide and KOH in a weight ratio of 1:4.3, andheating it at 800° C. for 1 hour in the furnace under a nitrogenatmosphere. Then, activated carbon 2a which was to be used as thepositive electrode material was obtained by washing the activated carbonunder stirring for 1 hour in a diluted hydrochloric acid, theconcentration of which was adjusted to 2 mol/L, subsequently washingwith distilled water under boiling in which pH holds in a range of pH 5to 6, and then drying it.

The fine pore distribution in the resulting active carbon 2a wasmeasured using a fine pore distribution measurement apparatus(AUTOSORB-1, AS-1-MP), manufactured by Yuasa Ionics Co. Ltd., and basedon the desorption isotherm, the mesopore volume and micropore volumewere determined by the BJH method and the MP method, respectively. Thespecific surface area was determined by the BET one-point method. As aresult, the BET specific area was 3,120 m²/g, the mesopore volume (V₁)1.33 cc/g, micropore volume (V₂) 1.88 cc/g, and V₁/V₂=0.71.

A slurry having a solid concentration of 14% by weight was obtained bymixing 63.9 parts by weight of activated carbon 2a as the positiveelectrode active material, 30.5 parts by weight of lithium carbonatehaving an average particle diameter of 5.3 μm as the alkali metalcompound, 6.3 parts by weight of ketjen black, and 6.3 parts by weightof PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone). Apositive electrode precursor was obtained by coating the resultingslurry on one surface of an aluminum foil (thickness of 15 μm) which wasused as the positive electrode power collector, drying, and pressing it.The thickness of the positive electrode active material layer in theresulting positive electrode precursor was 95 μm. A₁/B₁ of this positiveelectrode precursor was 0.44, and the amount A₁ of lithium carbonate perunit area was 32.0 g/m².

[Preparation of Negative Electrode]

The fine pore distribution of a commercial coconut shell activatedcarbon was measured using a fine pore distribution measurement apparatus(AUTOSORB-1, AS-1-MP, manufactured by Yuasa Ionics Co., Ltd., andnitrogen as an adsorbate. The specific surface area was determined bythe BET one-point method. Based on the desorption isotherm, the mesoporevolume and the micropore volume are calculated by the BJH method and theMP method, respectively. As a result, the BET specific area was 1780m²/g, the mesopore volume (V₁) 0.198 cc/g, the micropore volume (V₂)0.695 cc/g, and V₁/V₂=0.29, and the average fine particle diameter was21.2 Å.

A thermal reaction was carried out by putting 150 g of this coconutshell activated carbon in a cage made of a stainless steel mesh, puttingit on a stainless steel tray containing 270 g of coal-based pitch(softening point: 50° C.), and installing it inside an electric furnace(effective dimension of inside the furnace: 300 mm×300 mm×300 mm).Composite porous material 1 which was used as the negative electrodematerial was prepared by heating it under a nitrogen atmosphere,increasing the temperature up to 600° C. over the period of 8 hours, andholding it at the same temperature for 4 hours. After cooling down thecomposite porous material to 60° C. by natural cooling, it was taken outfrom the furnace.

As for resulting composite porous material 1, the measurement of thefine pore distribution was carried out in similar manner to that of thecoconut shell activated carbon, and the results were obtained asfollows: the BET specific area was 262 m²/g, the mesopore volume 0.180cc/g, the micropore volume 0.0843 cc/g, and V₁/V₂=2.13.

A slurry was obtained by mixing 83.4 parts by weight of the compositeporous material 1, 8.3 parts by weight of acetylene black, 8.3 parts byweight of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone).Next, a negative electrode was obtained by coating the resulting slurryon one surface of an electrolytic copper foil having a thickness of 10μm, which was to be used as the negative electrode power collector,drying, and pressing it. The thickness of the negative electrode activematerial layer in the resulting negative electrode was 43 μm.

[Fabrication of Nonaqueous Hybrid Capacitor]

One sheet of the positive electrode precursor prepared above was cut outto a size of 2.0 cm×2.0 cm (4.0 cm²), and one sheet of the negativeelectrode prepared above was cut out to a size of 2.1 cm×2.1 cm (4.4cm²). Further, one sheet of a separator made of polyethylene(manufactured by ASAHI KASEI E-materials Corp., thickness 20 μm) wasprepared. An electrode laminated body was fabricated by laminating themin the order of the positive electrode precursor, the separator, and thenegative electrode. For this electrode laminated body, A₁ was 32.0 g/m²,G₁ 22.0 Ah/m², and thus the value of A₁/G₁ was 1.45 g/Ah, all of whichhave been confirmed to satisfy the requirement of the present invention.

An electrochemical cell was prepared by putting this laminated body intoa container formed with a laminate film composed of polypropylene and analuminum foil, pouring into it the electrolytic solution in which LiPF₆was dissolved in a mixed solvent of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) in a weight ratio of 1:2 at a concentration of1.5 mol/l.

(Voltage Applying Step (Pre-Doping Step))

In order to obtain the nonaqueous hybrid capacitor of Example 62, forthe resulting electrochemical cell, after charging up to 4.5 V under theconstant current of 2 mA at an environment of 25° C. by using a chargingand discharging apparatus (TOSCAT-3100U), manufactured by ToyosystemCorp., followed by charging under the constant voltage at 4.5 V for 72hours, lithium ions were pre-doped to the negative electrode.

Three pieces, in total, of the nonaqueous hybrid capacitor of Example 62were prepared in a similar manner to that above.

[Measurement of Time Constant after Pre-Doping]

For the first piece of the nonaqueous hybrid capacitors fabricatedabove, discharging was carried out down to 2.2 V in a thermostat chamberset at 25° C. Next, after charging under the constant current of themaximum current of 2 mA as well as the constant voltage of the maximumvoltage of 3.8 V was carried out for 1 hour, constant discharging at thedischarging current of 10 mA was carried out down to 2.2 V.

The discharging capacitance at this time was 2.48 F, the direct currentresistance value was 0.69Ω, and the time constant (2F) was calculatedfrom them to be 1.71 sec.

By using the following values such as the voltage value at 0 second(initiation of discharging) denoted as V₀, V₁ corresponding to thevoltage at 0 second which was obtained by extrapolating the voltagesfrom during 1.0 to 2.0 seconds to 0 second, and the discharging acurrent value I, then a direct current resistance value expressed by thenumerical equation of (V₀−V₁)/I was calculated.

[Presence or Absence of Deposition of Metal Lithium]

It has been confirmed by checking the surface of the negative electrodeafter disassembling the nonaqueous hybrid capacitor in an argon box thatthe metal lithium did not deposit on the surface.

[Charging and Discharging Cycle Characteristics Under High Load]

The second piece of the nonaqueous hybrid capacitor was installed in athermostat chamber set at 25° C., and by setting a charging current to0.2 A as well as a discharging current to 0.2 A using a charging anddischarging apparatus (ACD-01), manufactured by Asca Densi Co., Ltd.,high-load charging as well as discharging of the capacitor at theconstant current for both charging and discharging in the range betweenthe lower limit voltage of 2.2 V and the upper limit voltage of 3.8 Vwas repeated 5,000 cycles. After the high-load charging and dischargingcycle were completed, the time constant was calculated by measuring thedischarging capacitance and the direct current resistance in a similarmanner to that of the previous method.

[Storage Characteristics at High Temperature]

The third piece of the nonaqueous hybrid capacitor was installed in athermostat chamber set at 25° C., and charging under the constantcurrent of the maximum current of 2 mA as well as under the constantvoltage of the maximum voltage of 3.8 V was carried out for 1 hour byusing a charging and discharging apparatus (ACD-01), manufactured byAsca Densi Co., Ltd. Next, the nonaqueous hybrid capacitor was immersedin Florinert FC40 (trade name, produced by 3M Co., Ltd., afluorine-based inert liquid), where the temperature was adjusted to 25°C., and the volume of the nonaqueous hybrid capacitor was measured.After this, it was stored for 30 days in the thermostat chamber set at80° C. After the elapse of the 30 days, it was stored in the thermostatchamber set at 25° C. for 2 hours, and then the volume of the nonaqueoushybrid capacitor was measured in a similar manner to the above method.

By comparing the volumes before and after storage at 80° C. for 30 days,it was confirmed that the gas generation volume during storage was only0.1 cc.

Examples 63 to 70 and Comparative Examples 48 to 55

Each of positive electrode precursors for nonaqueous hybrid capacitorswas fabricated in a similar manner to that described in Example 62except for changing an amount of lithium carbonate in the positiveelectrode precursor and an amount of a slurry for the positive electrodeto be coated on the positive electrode power collector.

Negative electrodes for the nonaqueous hybrid capacitors were preparedin a similar manner to that described in Example 62 except for adjustingan amount of a slurry for the negative electrode which was coated on thenegative electrode power collector.

Each of the nonaqueous hybrid capacitors was fabricated and evaluated ina similar manner to that described in Example 62 except for using theresulting positive electrode precursors and the negative electrodes. Theevaluation results are shown in Table 5.

TABLE 5 Time const. after charging/ Time const. Deposition dischargingafter of cycle under A₁ G₁ B₁ A₁/G₁ pre-doping metal high load [g/m²][Ah/m²] [g/m²] [g/Ah] A₁/B₁ [sec] Li [sec] Exp. 62 32.0 22.0 72.9 1.450.44 1.71 No 1.79 Exp. 63 32.0 17.2 72.9 1.86 0.44 1.65 No 1.72 Exp. 6432.0 29.8 72.9 1.07 0.44 1.77 No 1.83 Exp. 65 24.2 22.0 72.9 1.1 0.331.4 No 1.84 Exp. 66 42.1 22.0 72.9 1.91 0.58 1.81 No 1.87 Exp. 67 32.022.0 35.4 1.45 0.90 1.89 No 1.95 Exp. 68 18.5 17.2 72.9 1.08 0.25 1.74No 1.89 Exp. 69 32.0 17.2 35.4 1.86 0.90 1.72 No 1.81 Exp. 70 25.3 17.252.2 1.47 0.48 1.76 No 1.87 Com. 15.1 22.0 72.9 0.69 0.21 2.26 No 2.67Exp. 48 Com. 17.3 22.0 52.2 0.79 0.33 2.05 No 2.48 Exp. 49 Com. 12.417.2 52.2 0.72 0.24 2.11 No 2.87 Exp. 50 Com. 15.8 17.2 52.2 0.92 0.301.97 No 2.65 Exp. 51 Com. 46.7 22.0 52.2 2.12 0.89 2.2 Yes 2.33 Exp. 52Com. 46.7 22.0 72.9 2.12 0.64 2.38 Yes 2.52 Exp. 53 Com. 42.1 18.2 35.42.31 1.19 2.65 Yes 2.78 Exp. 54 Com 46.7 18.2 35.4 2.57 1.32 3.02 Yes3.18 Exp. 55

Comparative Example 56

The nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 62 except for using lithium oxalate instead oflithium carbonate as the lithium compound. The storage characteristicsof the resulting storage element, at the high temperature were evaluatedby a similar method described in Example 62, and it has been confirmedthat 1.8 cc of gas was generated.

It has been understood by comparing Example 62 with Comparative Example56, that gas was generated during storage at the high temperature whenlithium oxalate was used instead of the lithium compound specified inthe present invention. It is considered that, in the case of the lithiumcompound having low oxidation potential and being represented by lithiumoxalate, the lithium compound does not react completely in the voltageapplying step, thereby gas was generated due to the lithium compoundremained in the storage element.

Example 71

A nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 62 except for carrying out charging under theconditions of constant voltage of 4.2 V and an environment of 60° C. for168 hours as those in the voltage application step (pre-doping step). Acharging current was observed in the resulting nonaqueous hybridcapacitor by charging at 4.2 V, from which it has been confirmed thatpre-doping of lithium ions to a negative electrode proceeded.

Comparative Example 57

A nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 62 except for carrying out charging under theconditions of the constant voltage of 4.1 V and an environment of 60° C.for 168 hours as those in the voltage application step (pre-dopingstep). The resulting nonaqueous hybrid capacitor did not operate as thestorage element.

Comparison of Example 71 and Comparative Example 57

By comparing Example 71 with Comparative Example 57, it has beenunderstood that the voltage of equal to or higher than 4.2 V ought to beapplied to the nonaqueous hybrid capacitor in order to carry outpre-doping of lithium ions to the negative electrode by decomposing alithium compound contained in a positive electrode.

Example 72 [Preparation of Positive Electrode Precursor]

A positive electrode precursor having thickness (37 μm) of the positiveelectrode active material layer was obtained in a similar manner asdescribed in Example 61 except for using 70.0 parts by weight ofacetylene black and 20.0 parts by weight of lithium oxide having anaverage particle diameter of 23 μm, instead of lithium carbonate as thelithium compound. A₁/G₁ of this positive electrode precursor was 0.25,and the amount, A₁ of lithium oxide per unit area of the positiveelectrode precursor was 7.0 g/m².

[Preparation of Lithium-Type Storage Element]

An electrode laminated body was fabricated by a similar method asdescribed in Example 61 except for using the positive electrodeprecursor described above. For this electrode laminated body, A₁ was 7.0g/m², and G₁ was 5.7 Ah/m², from which A₁/G₁ can be calculated as 1.23,and it has been confirmed that the requirement of the present inventionis satisfied.

The following nonaqueous hybrid capacitors were fabricated by a similarmethod as described in Example 61 by using the electrode laminated body.

<Evaluation of Voltage Application Step (Pre-Doping Step)>

Pre-doping of lithium ions to the negative electrode in the resultingelectrochemical cell was carried out by a similar method as described inExample 61. The charging curves (the current value, the voltage change,the positive electrode potential change, and the negative electrodepotential change) at this time are shown in FIG. 3.

In Example 72, too, by a similar manner as described in Example 61, anelectric current of 268 mAh/g flowed in the negative electrode which waslarger than the reacted amount (10 mAh/g) of the electrolyte containedin an electrolytic solution, and the negative electrode potential waslowered to 0.2 V, from which a sufficient amount of lithium ions wasable to be pre-doped to the negative electrode. As described above, ithas been confirmed that even in the case that lithium oxide was used asthe lithium compound, lithium ions can be pre-doped to the negativeelectrode by allowing oxidative decomposition of a lithium compound toproceed in a similar manner to the case of lithium carbonate, and byreducing the generated lithium ions at the negative electrode.

Examples 73 to 81 and Comparative Examples 58 to 65

Each of positive electrode precursors of nonaqueous hybrid capacitorswas fabricated in a similar manner as described in Example 62 except forusing lithium hydroxide as the lithium compound, and changing an amountof lithium hydroxide in the positive electrode active material layer andan amount of a slurry to be coated on to the positive electrode powercollector.

Negative electrodes of the nonaqueous hybrid capacitors were fabricatedin a similar manner as described in Example 62 except for adjusting anamount of the slurry for the negative electrode to be coated on to thenegative electrode power collector.

Each of the nonaqueous hybrid capacitors was fabricated and evaluated bya similar method as described in Example 62 except for using theresulting positive electrode precursors and the negative electrode. Theevaluation results are shown in Table 6.

TABLE 6 Time const. after charging/ Time const. Deposition dischargingafter of cycle under A₁ G₁ B₁ A₁/G₁ pre-doping metal high load [g/m²][Ah/m²] [g/m²] [g/Ah] A₁/B₁ [sec] Li [sec] Exp. 73 31.0 22.0 74.5 1.410.42 0.00 No 1.76 Exp. 74 31.0 17.2 74.5 1.80 0.42 0.00 No 1.71 Exp. 7531.0 29.8 74.5 1.04 0.42 0.00 No 1.94 Exp. 76 25.4 22.0 74.5 1.15 0.340.00 No 1.84 Exp. 77 43.2 22.0 74.5 1.96 0.58 0.00 No 1.89 Exp. 78 31.022.0 36.2 1.41 0.86 0.00 No 1.91 Exp. 79 18.9 17.2 74.5 1.10 0.25 0.00No 1.92 Exp. 80 31.0 17.2 36.2 1.80 0.86 0.00 No 1.86 Exp. 81 22.7 17.255.1 1.32 0.41 0.00 No 1.87 Com. 13.4 22.0 72.9 0.61 0.10 2.26 No 2.76Exp. 58 Com. 17.1 22.0 55.1 0.78 0.31 2.05 No 2.53 Exp. 59 Com. 13.117.2 55.1 0.76 0.24 2.11 No 2.80 Exp. 60 Com. 15.1 17.2 55.1 0.88 0.271.97 No 2.42 Exp. 61 Com. 48.1 22.0 55.1 2.19 0.87 2.20 Yes 2.31 Exp. 62Com. 48.1 22.0 74.5 2.19 0.65 2.38 Yes 2.49 Exp. 63 Com. 45.3 18.2 36.22.49 1.25 2.65 Yes 2.75 Exp. 64 Com 48.1 18.2 36.2 2.64 1.33 3.02 Yes3.13 Exp. 65

Example 82 [Preparation of Electrolytic Solution]

After a solution was prepared by mixing ethylene carbonate (EC) andmethyl ethyl carbonate (EMC) in a weight ratio of 1:2, and dissolvingLiPF₆ to 1 L of the mixture so as to adjust the concentration of LiPF₆to be 1.5 mol/L, by adding 3% by weight of ferrocene as an additive forthe electrolytic solution with respect to the solution, an electrolyticsolution of this Example 82 was prepared.

[Preparation of Nonaqueous Hybrid Capacitor]

A nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 62 except for carrying out charging by using theelectrolytic solution under the conditions of the constant voltage of4.2 V and an environment of 45° C. for 168 hours as those in the voltageapplication step (pre-doping step).

In the voltage application step a charging current was observed bycharging at 4.2 V, from which it has been confirmed that pre-doping oflithium ions to the negative electrode proceeded.

Example 83

A nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 82 except for using 3% by weight of titanocenedichloride, instead of ferrocene as the additive for the electrolyticsolution.

In the voltage application step a charging current was observedaccompanied with charging at 4.2 V, from which it has been confirmedthat pre-doping of lithium ions to the negative electrode proceeded.

Example 84

A nonaqueous hybrid capacitor was fabricated by a similar method asdescribed in Example 82 except for using 5% by weight of 12-crown4-ether, instead of ferrocene as the additive for the electrolyticsolution.

In the voltage application step a charging current was observedaccompanied with charging at 4.2 V, from which it has been confirmedthat pre-doping of lithium ions to the negative electrode proceeded.

Evaluation of Examples 82 to 84

In Examples 82 to 84, pre-doping of lithium ions to a negative electrodeproceeded by the voltage applying step at an environment of 45° C. Thereason is as follows: Activation energy of an oxidation reaction of thelithium compound lowered by addition of Lewis acid or Lewis base to theelectrolytic solution, and thus the temperature required in pre-dopingof lithium ions lowered.

INDUSTRIAL APPLICABILITY

The positive electrode precursor of the present invention is suitablefor use such as a positive electrode precursor of a nonaqueous hybridcapacitor which is used in a power regeneration system in automotivehybrid drive system, in which charging and discharging cyclecharacteristics under a high load are required; a power load smoothingsystem in natural power generation such as solar power generation, windpower generation, microgrid, and etc.; a non-service interruption powersource system in production facility in a plant, etc.; a non-contactpower supply system aiming at microwave power transmission, smoothing ofvoltage variation of electrolytic resonance, and energy storage; anenergy harvest system aiming at utilization of power generated byvibration power, and etc. The nonaqueous hybrid capacitor can be usedfor a storage module, for example, by connecting multiple pieces of thenonaqueous lithium storage elements in series or in parallel. Thenonaqueous hybrid capacitor of the present invention is preferablyapplied, and used as the lithium ion capacitor since the maximum effectof the present invention can be achieved.

What is claimed is:
 1. A nonaqueous hybrid capacitor comprising anelectrode laminated body, wherein the electrode laminated bodycomprises: a positive electrode precursor; a negative electrode; and aseparator, wherein the positive electrode precursor comprises: apositive electrode active material containing a carbon material; and analkali metal compound, wherein the positive electrode precursor has onesurface and another surface, and a positive electrode active materiallayer is present at the one surface or both the one surface and theother of the positive electrode precursor, wherein 5≤A≤35, when A (g/m²)is a weight of the alkali metal compound in the positive electrodeactive material layer at the one surface of the positive electrodeprecursor, wherein 10≤B≤100 as well as 0.20≤A/B≤1.00, when B (g/m²) is aweight of the positive electrode active material in the positiveelectrode active material layer, wherein 1≤C≤20, when C (m²/cm²) is aspecific surface area measured by the BET method using nitrogen as anadsorbate at the one surface of the positive electrode precursor perunit area of the one surface of the positive electrode precursor,wherein A/G₁ is equal to or larger than 1.0 (g/Ah) and equal to orsmaller than 2.0 (g/Ah), when G₁ (Ah/m²) is a Capacitance Per Unit Areaof the One Surface of the Negative electrode.
 2. The nonaqueous hybridcapacitor according to claim 1, wherein A/G₁ is equal to or larger than1.49 g/Ah and equal to or smaller than 1.91 g/Ah.
 3. The nonaqueoushybrid capacitor according to claim 1, wherein 0.116≤C/B≤0.5.
 4. Thenonaqueous hybrid capacitor according to claim 1, wherein the separatorincludes a polyolefin film.
 5. The nonaqueous hybrid capacitor accordingto claim 4, wherein the polyolefin film includes polyethylene orpolypropylene.
 6. The nonaqueous hybrid capacitor according to claim 1,wherein the alkali metal compound is at least one selected from thegroup consisting of an alkali metal carbonate salt, lithium oxide, andlithium hydroxide.
 7. The nonaqueous hybrid capacitor according to claim1, wherein 5≤X≤50, when X % by weight is a weight ratio of the alkalimetal compound in the positive electrode active material layer of thepositive electrode precursor, and wherein 5≤S₁≤60, and 0.50≤S₁/X≤2.00,when S₁% is an area of oxygen mapping whose luminance values arebinarized based on the average luminance value in the oxygen mapping ofthe one surface of the positive electrode precursor measured by ascanning electron microscope—an energy-dispersive X-ray spectroscopy(SEM-EDX).
 8. The nonaqueous hybrid capacitor according to claim 7,wherein 5≤S₂≤60, and 0.50≤S₂/X≤2.00, when S₂% is an area of oxygenmapping whose luminance values are binarized based on the averageluminance value in the oxygen mapping obtained by SEM-EDX measurement ofa cross section of the positive electrode precursor where the crosssection is prepared by irradiating the positive electrode precursor witha broad ion beam (BIB).
 9. The nonaqueous hybrid capacitor according toclaim 1, wherein 0.3≤D≤5.0 and 0.5≤E≤10 are satisfied, when D (μL/cm²)is the mesopore volume of the positive electrode precursor per a unitarea derived from fine pores having a diameter of equal to or largerthan 20 Å and equal to or smaller than 500 Å of the one surface of thepositive electrode precursor, the diameter is calculated by the BJHmethod at the one surface of the positive electrode precursor, and E(μL/cm²) is the micropore volume per unit area derived from fine poreshaving a diameter of smaller than 20 Å, the volume of which iscalculated by the MP method.
 10. The nonaqueous hybrid capacitoraccording to claim 1, wherein the alkali metal compound is in the formof particles, and the average particle diameter of the particles of thealkali metal compound is equal to or larger than 0.1 μm and equal to orsmaller than 10 μm.
 11. A production method for the nonaqueous hybridcapacitor according to claim 1, comprising the following steps of: (1) astep of accommodating the electrode laminated body into a casing; (2) astep of pouring into the casing a nonaqueous electrolytic solutioncontaining electrolytes including lithium ions; and (3) a step ofdecomposing the alkali metal compound by applying a voltage between thepositive electrode precursor and the negative electrode, wherein thevoltage is equal to or higher than 4.2 V.
 12. The production method forthe nonaqueous hybrid capacitor, according to claim 11, wherein thenonaqueous electrolytic solution comprises: Lewis acid in an amount ofequal to or more than 0.5% by weight and equal to or less than 5% byweight; and/or a crown ether in an amount of equal to or more than 1.0%by weight and equal to or less than 10.0% by weight.
 13. A storagemodule comprising the nonaqueous hybrid capacitor according to claim 1.